I have a 2003 E39 530D Sport Auto and have recently bought one of these Ecotune Decat downpipes http://www.ebay.co.uk/itm/ST-STEEL-B...item3cc0764d3a

I have had it fitted and I now have a problem. the exhaust doesnt seem to be blowing but I am hearing an awfull lot of Turbo chatter and whistling up about 2500RPM then it seems as if something closes and the noise stops. It sounds like a Cossie with a big Foam induction kit and it really annoying LOL
The mechanic has had another look and says he cant see anything wrong but it cant just be because i dont have the cats anymore surely. Is there anything he might have broken/disturbed etc around the downpipe?

Any advice would be good, people actually turn round when the hear me whistling down the road now, hardly discrete LOL