I transplanted a stock 1987 350 TPI into an older Camaro changing nothing about the engine and it continued to run great and pass inspection easily. During the transplant I changed to a Painless Wiring TPI harness and it worked great. It had 25,000 miles on it. Slowly, over about two years and 20,000 miles later, it began to run leaner even when cold. Now it runs very lean and can barely stay running: the spark plugs are white, the car is not as fast, it knocks, and the NOx is high at the tailpipe. What can I do to get the engine to run richer since the computer will not? I already changed the O2 sensor and other tune-up parts. There are two new cats on the car. I will take any ideas.
Jason

I changed the fuel pump to an external electric Accel that matched the stock specs of a TPI internal pump; there is enough pressure. I do not have a scanner but I think I have to hire someone with one to make sure it is reading from the sensors. The ECM shows no trouble codes. I never made and changes while it started running lean.

 

did you change the fuel pump during the swap and check the pressure? Can you get a scanner to read what the ecm is seeing, is the injector pulse width opening/is it getting readings from the TPS/MAF?/MAP? sensors?