Newbie here.I just bought a 2004 a4 GTO it has cai,catless mids,and a catback,the cel is on because of the cats.My car runs like a dog down low but at higher rpms it screams would this be caused by the cel.If so would having the car tuned fix the problem.

Thanks Matt.

 

The check light may be on for other reasons,

Best way probably is have a GM workshop with Tech-2 look at it and see what the codes are and then take it from there.