Did the key dance.....code 21....only appeared after i got my exhaust done...Is it the cat?? or something different??

Code 21 is for an oxygen sensor. Since they did the exhaust, check the O2 sensor underneath the middle of the car after the cat, maybe they didnt put it back in right or something.

Chris Jones
1997 Dodge Avenger ES 5spd
"Racing Your Honda Is Like Running In The Special Olympics.....Even If You Win You're Still Retarded!!!

Chris Jones
1997 Dodge Avenger ES 5spd
"Racing Your Honda Is Like Running In The Special Olympics.....Even If You Win You're Still Retarded!!!

could be either upstream or downstream, check connections for both.

Did you just get that cat put on there, if so that could be the problem, sometimes there is still oil etc. in the cat that will burn off and clog the 02 sensor, but check the connections first

Supposedly they say to leave the downstream 02 off for atleast a week or so to let all the crap in the cat burn off and not hurt the o2 sensor

1998 dodge avenger 4 cyl AT
Mods are:
Not enough