Dies when shifted into drive

I am working on a 1997 chevy Cavalier 2.2L. he replaced the ENGINE/TRANS and ECU. His car had the 3 speed trans and he put the 4 speed in it.

Well initially he called my because he was ahving a problem starting the car because the ANTI-THEFT SYSTEM was active. So I told him how to get that fix, with resetting/relearning the code and the car starts fine now, but whenever he puts it in DRIVE the car stalls, but in reverse it runs fine only when shifted to any of the FOWARD DRIVING GEARS does it stall.

Any suggestions ideas?

I was going to say your converter lock up solenoid is stuck, but that shouldn't be the problem since reverse is ok.

Could be a wiring problem, rocking the engine in the drive direction could pull a frayed/broken wire apart. Wiggle all the wires while it's idling in park and see if you can get it to die. Open the harness up where pulling it makes the engine die.