I am going to get my exhaust all redone this weekend. I was wondering what size piping I should get, Im not sure what the stock size is, Im guessing duel 2 1/4" so ill probably bump it up to 2 1/2" and change the mufflers and put bigger resonators and redo the y-pipe. Im also not sure but does a 98 GS400 have 3 cats or just one and where is the sensor? I just got the car two weeks ago and havent looked under it yet. If anyone knows please let me know. Thanks

 

i dunno, but u could call steve and ask what the sizing is of the trd exhaust to get an idea