MrMoose

Nobody debates that. The question is whether spraying cleaner into the intake (which does hit the valves, even on a DI engine) is effective.

Like I said, I've personally seen good results from professional cleanings of that sort. Can't tell you if the "mechanic in a can" products work as well (or at all), but the potential exists for them to have an effect.

BondJ

Cans of ‘instant rebore’ and other such crap have been on sale for years. My advice, don’t bother…

CaymanCarver

I'd add these products can potentially gunk up the O2 sensors.

okie981

And/or clog catalytic converters? I don't know if this is true, but have wondered about it.