hi I have a silverado 1994 350 tbi my proble is misfire at idle and when the timing advance.I have change 2 engine in 2 week cause the first i buy was not good.new plug and wire cap and test a used coil and ignition module but same problem.this engine have run very goud for 1 day and after the proble have star slowly hard to start now.i have change the tbi cause it was more lean on a injector now gas is ok but misfire stay.I have chek the timing and it was ok 0 btdc with tan wire unplug (timing advance) this engine is supose to be stock.I have see the timing light stop to flash stedy when I open the trotle to make advance the timing (electronic controled) no code in ecm i dont know were to find now thank for your help sorry normaly i speak french