12 valves had cats 24 valves had the resignator. If its a 04.5 it wont match up they had 4" from the factory. Im not sure if early 04s had a 4" or not. If they didnt then it might be possable.

 

'04s have 4" the early '03s have 3" or 3.5" on the down pipe. Tomeygun from TDR replaced an adaptor on his 03 turbo with one from an 04 to run a 4". I agree with the 24 valves upto 04.5 models which cats came back in style.