I had the same problem with my -93 Esc Cos when I put an AB chip in it for some years ago.
After many hours with testing and replacing all the other components.... I send the ECU to Mr Bajoo. When I got it back everyting works perfect... He would't tell what he had done with it, but the same anyway... the car went very well after.

This was his chip for 803's 3 bar P8 ecu

If noting else matter, contact Mr Bayjo

Jan Erik
Norway