Slight slipping while idle and driving

My vehicle started making a banging sound around the fan and idle pulley area. Within the next few days it progressively got worse, as in when driving next day started to bog down a little while driving and then didn't start at all. It turned over but didn't fully start. We changed tension-er pulley, spark plugs and serpentine belt. When we started it again, the sound was gone and started slightly slipping or misfiring while driving. AutoZone said cylinder 1 and 4 were misfiring, so we changed both coil packs. Still having the same problem. We have put $445.00 total between parts and labor and can't really keep affording to play the guessing game with no positive results.