When I hit about 5000 to 5500 rpm's I hear a whistling noise that subsides as rpm's get higher. I am pretty sure that the whistling noise wasn't there before the mods, which were done all at the same time (BSR PPC, BSR exhaust and BMC air filter).<p>I was at the dealer's today to get something and told them about it. They checked the car, said I need not worry about it but pointed to either the BMC air filter or the ppc as the culprit (which was to be expected of course).<p>I exchanged the air filter with the stock and it still whistles. I didn't have time to uninstall the ppc and check if the whistling is still there (I will do that on Friday hopefully) but I was wondering if any of you with BSR's ppc have noticed this whistling noise as well. Maybe it has to do with the turbo pressure?