STG 3 Bar Multichip Installation Instructions


Install 3 bar MAP sensor (not included) either in place of or near original 2 bar.  For location and specifications of the 2 bar sensor refer to the Sylcone or Typhoon shop manual   Part number for the 3 bar map sensor is 1604-0749 (GM/AC Delco sensor assembly, stock usage was 1989 Turbo Trans Am).  The 3 bar sensor is a necessary component, and can be found for $45 - $90.  There have been mishaps of people receiving 2 bar map sensors instead of 3 bar sensors.  An easy way to check if you have the correct sensor is to observe the stock boost gauge in your dash, as its readings will be incorrect with the 3 bar sensor.  The stock boost gauge will not cross from green to yellow at 0 psi, you’ll now remain in the green section when crossing into boost (reading as vacuum).   Finally, the 3 bar programs are tuned for a static (no vacuum) fuel pressure of ~50 psi at idle.


Installation of hardware:  Locate the protective sleeve for the ribbon cable and route the ribbon cable through it.  This step is optional but recommended especially if you are going to route the cable behind the dash to a remote location.  One some units this may have already been done prior to shipping.  Remove stock memcal (chip) from ECM.  ECM is located behind the glovebox, accessible by removing the plastic panel under the passenger side dash, and passenger side kick- panel.  Carefully plug the memcal into the multichip piggyback prom carrier with the key (tab) on the MEMCAL sliding into the slot cut into the piggyback carrier circuit board.   See photo below.







It is recommending that you trim the left memcal retaining clip (the one closest to the top of the ECM).  The idea is to trim off enough from the edge as to not crimp the ribbon cable when the carrier is installed into the ECM and to allow the carrier to seat fully into the connector.  It has been noted that it is possible in some ECM’s to install the chip completely without trimming this clip, but I personally recommend trimming.  The ECM cover will prevent the memcal/carrier from working loose.  Plug the carrier into the connector in the ECM from where you removed the memcal.  The memcal will be toward the side of the ECM where the wiring harness mates.  If you have the carrier in properly, the two retaining clips will close as you push the carrier into the connector.


At this point, you can turn the ignition key on, with engine off.  Make sure the check engine light stays on steady, which is normal.  If you have a scan tool, you can read the prom ID’s by toggling the switch through the positions, with “0” being the first.  These steps will verify that all is working properly.  You can start the truck at this point and the check engine light should go off and the truck should run normally.  You can try the security position if you have this option and the truck will not run.   The valet program will not run the intercooler pump, which you can also verify if you wish.  This program also has the timing advance reduced significantly and a 4000 rpm limit, making it a part throttle only program.  Programs can be changed while truck is running or shut down.


Once you’re satisfied that all is correct, shut down the vehicle and run the ribbon cable/switch to wherever you want to locate it.  For the 4-1 chip, or 8-1/10-1 upgrades, I recommend running the cable up behind the dash and into the glovebox through the removable panel in the back of it.  You can use the supplied two sided tape to attach the switch to the side of the glovebox.  Replace the glovebox panel making sure that you don’t overtighten the screws, crimping the ribbon cable.  Replace the cover on the ECM also making sure not to overtighten the screws and crimping the ribbon cable.  Re-install the ECM up behind the dash and you’re done.


This STG product is intended for off-road use only and is not legal for use on public highways or roads.  STG and its distributors assume no responsibility or liability for damage or injuries which may result from the use or installation of this product.  Take proper precautions before experimenting with boost levels and running the street/strip and strip chip with pump gas.  93 octane (R+M)/2 is the recommended level for the street program, but this will vary from vehicle to vehicle.  Unless there is a problem with the vehicle, 93 will be safe on any truck.  Some will find that lower octane is sufficient, especially if the turbo and/or intercooler has been upgraded.  This is the responsibility of the user to determine.  The street/strip chip can be used by some with pump gas at lower boost levels (16-17 and below).  The only sure way to determine this though is to monitor the engine parameters with a scan tool.  Safe boost and octane levels will vary from vehicle to vehicle.   An accurate boost gauge is highly recommended for any Typhoon/Syclone, otherwise you’re just guessing at boost levels


If your boost levels vary significantly from what is programmed into the chip, there are several possible causes.  It is normal for boost levels to vary between  +/- 0.5 psi from the levels indicated on the boost setting sheet.  One cause for significant variance could be that the wastegate rod is out of factory spec.  This can be changed by lengthening the rod (lowering boost) or shortening the rod (raising boost).  Typically, an out-of-adjustment wg rod will result in a boost curve which either under or over-shoots the programmed level and then slowly creeps to the proper level.  Another cause of poor boost control is leaking vacuum hoses going to and from the turbo/wastegate/wastegate solenoid.  This typically results in overboost that may or may not be controllable.  If you suspect that your hoses are old and brittle, now is a good time to replace them.  Significant ignition retard will cause erratic boost control.  Also, keep in mind that the stock turbo and wastegate system was designed with the backpressure of the stock catalytic converter and muffler in mind.  Once these items are altered, it can effect the ability of the ECM to control boost.  The 3 bar chip will do a good job of compensating for these type of situations, but cannot compensate 100%.  One event in particular to be aware of for those using the stock turbo/wastegate who have altered exhaust systems, is acceleration while cruising resulting in a downshift to first gear.  The sudden rush of exhaust out of the engine is too much for the stock wastegate to bleed off and boost spikes are common in this situation.  This situation is not related to the 3 bar or any other chip but is a characteristic of the stock turbo system.  This can typically be remedied by enlarging the wastegate orifice or upgrading the turbo and wastegate.


The security program will not allow the truck to start when it is selected.  The valet program has the timing advance significantly reduced and the rpm limit set at 4000, effectively making it a part throttle only program.   EGR is in operation only in the Valet and 15 psi T1 program, it is disabled in all the others.


Trouble-shooting.  If the truck does not run properly there are few common installation mistakes.  First check that the memcal is plugged into the piggyback carrier correctly.  Make sure that the EPROM (black chip) is fully inserted in the socket.  Finally, make sure that the chip carrier/memcal combination is fully inserted in the ECM and the retaining clip isn’t binding the ribbon cable or preventing the chip from being fully inserted.  If these items check out then you’ll need to contact the names below.


Feel free to contact us at or for any questions concerning this product.  For more information go to and look for the link called “Technical”.  This site will also give information on the latest updates and additions to the chip lineup.