both
ive talked to all the best gtr tuners in our lovely country for my big power app and they all say the same thing.
Stock piping and stock bovs are the best way to go on a gtr... changing the piping will unfortunately increase turbo shuffling.
if u want to minimise it, got back to stock bovs n stock piping.
Ben from RacePace even laughed when i suggested that i wanted to run all hks piping from afms all the way to the plenum... stock is best