With estered gear, since the gear needs to be in the bloodstream before the esterase enzymes split the gear from it, site injection is a myth.
With unestered/injectable orals like injectable dbol/winny site enhancement is in theory possible and some say it exists. Personally I haven't tried it out yet but I know some knowledgeable and respected guys who say it has happened for them, I have no reason to disbelieve them