ive just fitted a hks exhaust and ive lost loads of power, it doesnt put you back in your seat no more, it feels like its not boosting, i put the old aftermarket (fujitabla or something, its only got a 2 1/2 inch tail pipe) one back on and its back to its lively self again, i thought hks was supposed to improve performance not take it away, any one had similar probs?or does anyone have any solutions to this?