Ok, I have an 02 svt focus. I noticed when I get to higher rpm's or when I step on it long enough on low rpm's my engine starts to sputter. I think it might be bad gas. I got worse as my last tank got closer and closer to empty. I just filled up now with new gas from a different station. I always use 93 octane. I put a fuel system cleaner in it as well. when I left it seemed to have less gargle and backfiring than than before. I do have the ORP so it does backfire normally. The sputtering still occured but not as violent. But it was just a short ride home. Can this be something else. Is it bad gas? If so, it should go away by the time I empty this tank. Any other info would be much appreciated.