My mate has recently finished modifiying his R34 GTT with majority brand name parts (garrett GT3540, Apexi power FC, Gready ProFec, Splitfire coils ect. ect) and tells me his cheap 600x300x76 actually 'wastes' around 3 psi of boost that turbo makes when number of tests were done.. Not sure how accurate this info is but may be food for thought..