Would fully strip throttle bodies myself if blast cleaning as stripping coatings off springs ect & extra areas for grit to hide in are not good. Also steel coated fittings need covering to avoid coatings being removed. Done a B6T rocker cover, Plenum & turbo pipe & came out ok but needed good cleaning & then an etching treatment was given to seal the casting surface as sand blasting tends to open the pores & allow moisture ingress & dirt retention thus easy oxidation ... Lasted well, looked better than the black peeling factory coating & easy to clean with a rag damped with WD40 ...