V8 Slayer

This question is about a Mustang, But its a general exhaust question..If I were to put on an offroad H-Pipe and NOT install the 02 Sims and run a check engine light for a little while until I shut it off with a tuner. Would this cause any problems with ECU readings or anything? Would my MPG drop or anything because of the SES?

2001NBMZ28

I wouldn't think rear 02 codes are going to cause any other problems, except for the SES.

Injuneer

Without knowing the details of the Mustang computer control system, which may be different than GM OBD-II logic, no one can answer that question.