i have a missfire i have been chasing even after engine rebuild .i have replaces all internal parts ( all new including cam ) i have installed the new conversion spyder injectors , new distributor , new crank sensor, new alt , new platinum plugs , wires,and coil . it has the org EGR valve and purge valve and map , i have replaced the maf with a known good used one . someone told me its the engine computer ?? i also have a irratic tach witch goes haywire and is all over the place ... please help !!!! i put a lot of money into this jimmy and i still cant drive it . no check engine light either . i can do a money donation towars any help .. dont have much money left due to the problems but a true answer is worth money to me =)