hi all, fitted new downpipe/flexi/cat last weekend [pre-cat removed] and was sounding braw, now it's making a whistling sound when accelerating and under load, almost like when a turbo pipe blows of the intercooler, when i'm up to speed and back off throttle it goes away, while the vecci isn't turbo'd, any ideas what it could be? exhaust ain't blowing at any flanges etc, tnx in advance..