fasty - I think it does. I mean I haven't taken the head off a car that's been dosed with FP, but my turbo sure behaved like it cleaned a load out of the combustion chamber....most all other fuel additives I tried, didn't seem to make much difference in this car, including Amsoil PI, Redline, etc...my injectors etc are new, the engine oil system is clean, so the only remaining build up was the combustion chambers.
Your mileage may vary, but the first few HIGH doses of FP resulted in lotsa crap flying out the back (if you know what I mean at full boost), but after that, suddenly I could use a notch lower octane fuel with less knockage at full boost. Something got cleaned....and it wasn't my wallet.