I have a 92 evo, compression is good 120, spark is great, i fliped coils, took apart s&s carb that looked great jets where right size, timing is great, every time i step on the gas the rear cylinder backfires LOUD, i am running out of things to check, so now i think its lifters or broken valve?? but i would not have compression if i has a valve spring that was broken or what??? anyone have a issue like this please help......i want to order lifters, but not sure if a failing lifter would cause a motor to backfire like this, or should i look at the valves???