I have used for years in many cars and I had good results, I even had a 96 Dodge Ram with no fuel filter, except the one that goes in the tank, and I used STP, I had great results.

 

seafoam is a good choice. you can get it at pep boys.

 

I had put a little bit of cheap stuff in the tank of my 4-wheeler. The spark arrestor screen at the end of the exhuast went from carboned to completely silver in a matter of an hour of hard riding....so you know if the exhaust gases have that effect, it will do some serious cleaning inside the engine with some hard running.