I have had my 1996 P32 chassis 454 TBI at GM since December. It is confirmed to be the high pressure, OBD 1 system, and all parts are correct and operational. When the MAP gets over 14 it stumbles and dies. They just called and have given up on trying to resolve the issue. Does anyone know of or could you direct me to someone that may know the fix?

My TBI system is a retrofit GM system assembled by Affordable Fuel Injection. It is very similar to yours I believe.

The OBD1 system can be checked with simple readers and will deliver error codes to them. Many auto stores will let you use them to read the codes.

If you really want to know what's going on you can get the ALDL cable and free software (WinALDL, etc) to download on the fly.

See here:
https://www.barthmobile.com/eve...243949977#3243949977

First thing: CHECK YOUR FUEL PRESSURE! The earlier computers (like this one) don't have a way to measure fuel pressure. As a result, pressure variations can cause all kinds of problems and the computer will never know or set a meaningful error code. If the pressure is not constant (mine should be 11-13 psi) the computer cannot sense it or fix it. I have had numerous problems with the fuel system but only a few with the OBD components.

Check for error codes.

Aside from fuel delivery, symptoms point to bad MAP or TPS maybe.

If your system is the higher pressure version, it may actually be the later OBD2 system. Different cable and software but also accessible.

Keep in touch, let us know what more you find.