Hi i have 92 RS L03 TBI and it seems to have a problem with backfiring and surging when under reasonable thorotle. Ive changed plugs, wires, dizzy cap, ecm, both fuel injectors, fuel pressure regulator,02 sensor and some other suff i cant think of at the moment. And when its cold i have to press down the throttle to start it and keep it running this is only when its cold but when its warmed up it idles at 700 but still surges backfires. The timing is set to 4*BTDC. I have no clue what to do next i thought it was something to do with the fuel but apperantly not? And also sometimes the check engine light will go on but then turn off a few moments later when its on its throwing the 02 sensor code which boggles me because it has a brand new 02 sensor on it...