on my gti when in low revs, theres a rattle that sounds like a shield but I've check the one around that cat and the one under the turbo. but it still rattles. any ideas as to what this could be?
Exactly what you think it is. Could also be the one on the rear of the car near the gas tank. you're likely missing one of the star washers (i don't know what they're called)
Could also be a failing cat. I had one go out on my New Beetle...sounded like a shield rattling so I assumed that's what it was. 6 months later CEL came on for the bad cat. No more rattling after replacement.