1994 Chevy Camaro Random missfire and backfire

My camaro has been acting up for quite some time now. It will randomly missfire and backfire as well. It doesn't matter if the car is warm or cold. Sometimes I can drive it for 15 minutes and it not missfire one time or backfire and others it can be very annoying as it will pop and chug down the road. I had it scanned for codes and it said MAF problems. So I tried cleaning it and that didn't work. So I bought a brand new one and that didn't fix it. The scanner said that my intake manifold pressure was 10 and they guy told me it should be 18. Plugs and wires are both a year old. I just replaced the coil. Also I started it up and let it idle and all of a sudden it backfired really loud and nearly gave me a heart attack. I don't want to keep throwing money at so please help!