It does have the 160 thermostat. I can swap in the original chip when I find "the safe place where I put it"  I have never had the plenum off, so is there a way to check for vacuum leaks of the lines going to the throttle body? I have a vacuum pump with gauge. Do these lines go to things with diaphragms that should hold a vacuum? I'm guessing that one goes to the fuel pressure reg, so probably yes to that, but what about the others.

Hello, I have a 90 TGP with 71,000 on it. It has a Jeff M crossover pipe, TG160 chip, and K&N filter, everything else is stock. The car runs great, for the most part, but has a hard time idling and stalls allot. Sometimes it will even stall while driving it (coasting down hill) or coming to a stop. Even in park it will only idle for a short time before stalling. I've done a search for stalling problems and have read through every thread to get some ideas, and checked all the common stuff. I've replaced the IAC, cleaned the throttle body, replaced the o2 sensor, checked for vacuum leaks, idle re-learn etc. It seems like the computer learns the idle ok but as soon as it goes closed loop, the problem begins. If I unplug the o2 sensor, causing the computer to stay in open loop, the car idles perfectly and would run all day in park or driving around. As soon as I plug in the o2 sensor and the computer goes into closed loop, the engine runs a little rough at any rpm, like a slight miss in the sound of the exhaust, but that is intermittent. Unplug the o2 and it's smooth as can be with perfect idle and no stalling. I'm leaning towards the ecm being the problem, but don't have one to swap in as a test. Before I commit to buying an ecm, I would like to hear any suggestions from other TGP owners. I have checked all the grounds, car has a new battery, TPS checks ok and was replaced a while back. The new o2 sensor is the AC Delco, and acts the same as the one that came off.  I am trying to sell the car but this stalling problem isn't helping me at all. Please offer any suggestions you may have. Thanks!

Quote from: Heartbeat1991 on June 03, 2015, 08:48:52 AM
Is it the original HD tranny rebuilt, or just a regular 4T60 rebuilt?

It's the original tranny that came with the car when I bought it new. It was sent out to Jasper for complete rebuild and the upgrades that they do. Cost me nearly $3000, and it only has a few hundred miles on it since then. The car has had allot of suspension parts replaced like ball joints, bushings, tie rod ends. I also replaced the headlamp assy's. The anti-lock brakes work well, accumulator is good. Has the Jeff M crossover pipe and performance chip as well.

Ultra rare 1990 Black with grey cloth interior. http://philadelphia.craigslist.org/cto/5045120550.html
Jeff M crossover pipe and chip. Newly rebuilt Jasper transmission. New headlight assy's, new tires and suspension parts. 

I am selling my 1990 TGP. Years ago Jeff M. told me it was ultra rare because of the grey cloth interior. He said if I ever wanted to sell it to let him know. Well the car is up for sale.   http://philadelphia.craigslist.org/cto/5045120550.html