Yeah, there's an interesting caviat here --- any coating on an internal engin part --- piston, valves inside headers etc. --- better stay on the part in a turbocharged application. Small flakes of misc. trash hittint a turbine impeller can do some significant damage when the turbine is spinning...
I've used the Techline on my current setup, external components only, headers, downpipe etc --- The car is a twin turbo Mitsu 3000gt. Fairly cheap and easy to apply, however, it did burn off of the turbine housings --- maybe an application problem, improper prep for example. Or maybe it just...
Polishing CC's or pistons is going to provide short term benefits at best --- as mentioned it only takes a few miles to build up a coating that would obscure your polishing job.
Why the adversion to coatings --- I was of the impression they were effective if properly done [ Swain seems to be a...