95flatblack

Some info on my truck. I have a 95 z71 350 auto. I put a Ederbrock multipoint on about 8 years ago. The throttle body is also used in conjunction with the multipoint. Problem is that there is a sight misfire and backfire through the exhaust. So far this is what I did in order to try to fix the problem. Installed new spark plugs which was needed, replace the EGR valve which had a hole in the diaphragm, check the resistance on both the fuel injectors and harness, used a stethoscope and listened to the fuel injectors and they were good, checked the timing and it was good. I have a one muffler with dual exhaust and using a playing card, tested to see if the card would be pulled towards the exhaust, which the right side of the exhaust did very slightly. So I thought that it might be a stuck exhaust valve. I poured water down the throttle running the engine in order to blow out some carbon. Very little smoke came out of the exhaust. Since that did not work, I put a bottle of engine cleaner and so far still have the problem. Any help with my problem would be appreciated. Thanks