1996 Plymouth Voyager I need help bad

Shakes or Wobbles problem
1996 Plymouth Voyager Two Wheel Drive Automatic 178951 miles

ok my van got wrecked on the drivers side which bent my gas tanka little (its a little complicated to put gas) well after I wrecked it the gas cap wouldnt go on so I drove it with a rag in it till I fixed it. In the process of waiting it rained one night which water got in my tank not thinking about it I still drove it. Well one night I was driving and it got jumpy and my engine knocked about 8 times and just died. When I got it to cool down just a litle it would start for a few seconds and knock again so I talked to a friend he suggested getting "Heet / 12 oz. ISO gas dryer and antifreeze " and so I did and it didnt do much so I replaces the fuel injector line, oxygen sensor, and upgraded the gas to primium. That happened about 3 months ago and yesterday it happened again it just started puttering and knocking and turned off. So I added a gas cleaner and let it cool down and it started after a hour and has ran since today mid day it knocked turned off and I let it sit and it turned back on. But I noticed when it starts to knock I put it in nutural and reved up the engine and it wanted to pop something out the muffler like it is clogged somewhere but I dont nkow where I checked the water its fine the oil is good what do I look for now