Fun with carbon

Hi NG!
I was helping my friend with his car the other day when he produced a
spray-can of liquid which allegedly, when sprayed down the intake, will
clean the carbon build-up in the combustion chambers. I happened to
have a couple of carbon-caked heads lying around from a 1600dp and
sprayed a little of the stuff directly on one to see what would happen
and the carbon literally melted away. (I feel like a commercial)
Can't get ahold of my friend or remember what the stuff was. Seems
like most spray-on stuff doesn't work that well. Any ideas what it
might be? Thanks!!!!

BM