How many KMs has the car done and has the cat been changed because as far as I knew, they wore out eventually so you mightn't be changing your earth kill ratio at all?
Camber arms, run a stretch on your 205/40/R19 tyres so the stretch will keep you away from the guards and look awesome. Run - 2 camber all round and you will be sorted, King Spring or Jamex super lows will sort you out with a tidy as drop too.
Jump in the car, open your door and sort of hang your head around the bottom of the car and give it a little rev. Could be a bit of rust or something in the exhaust. Had the same sort of issue with the girlfriend's E36, turns out on that one of the mufflers had been removed.