HELP 97 F150 4.6L Code P0305

I have checked MANY things. First off I pulled my plugs and checked compression and it was good. I replaced the plugs even though they looked good and were very clean. I still have a code P0305 and at one point I had a code P0300. CYLINDER MISFIRE. I changed my coil wires and coil packs. Same old crap. I added Iso-Heat to my tank thinking maybe fuel issue but no. I do run 93 oct in her. Air filter is clean. Replaced all o2 sensors at 100k miles and it has 150k miles on it now. This thing is driving me nuts. It runs like shit, coughs and sputters, and gets shit hole mileage. For a while I was getting a code saying EGR insurricient flow but we go that fixed with the egr lift sensor. Also, where I fill her up and the gas cap screws into is cracked. Could this be my prob? I don't know I am just upset with this thing! HELP

I'm no expert, but I do know that if you have air getting into your gas tank it will set off a code.

My gas cap sets off a code on my truck. I don't have a problem with sputtering though. In fact I have no problem other than the code going off so I just ignore it.

I wonder if you might be getting water into your tank?