'02 V6 3.8L Mustang sputtering and backfiring on acceleration...

Hey, I just joined the forums because I am having an issue with my Mustang. The stats are in the heading but please ask anything else that might be of help. About 3 months ago my Mustang starting sputtering and backfiring on acceleration pretty bad... It idles with no missing or sputtering at all and if I floor it it accelerates and runs witout any misses or sputtering either. It seems like it started all of the sudden. I have had it act like this before when it was raining and I went through a large puddle of water. It acted like that for about a week maybe 2 I assume while I worked the water out of the system. It was raining the night I noticed this but I also had someone slash my tires so I also am considered the possibility of them putting something in my gas tank.

So far I have used Heet everytime I have filled up with gas. I have made sure to get gas at a different station to make sure and rule that out. I have changed the fuel filter and spark plugs. My next step is the plug wires and I was debating on draining the tank and cleaning out though I would rather avoid that if not necessary (-Edit- I have now drained the tank and cleaned the strainer on the fuel pump and the issue still persists). Only thing I can think of is I do normally get gas at one station. The times I have filled up with gas elsewhere it has only been that one time before I refilled at my main station.

I would appreciate any ideas anyone might have with this issue...

-Edit- I just changed the plug wires and the issue persists.