I just put a flowmaster 40 series muffler, not a full catback, on my SS. I have been driving with this for a few days and just today my SES came on. I'm throwing MAF, intake, ect..basicly the entire induction codes. I do have a lid and smooth bellow, but have had those on for months now with no problems. Would the flowmaster throw these codes???? Could it be not getting enough or too much air for the factory sensors and is there a way to fix this? Oh! I have checked the induction system and it's fine...I don't see anything out of place. Thanks all.

 

I highly doubt the flowmaster is the problem. You need to go back over the intake again. Something is bound to be wrong with it. Is the maf backwards? Did you reconnect all the connectors properly? Did you break any wires? Do you have any leaks? Just throwing possiblities out there.....btw post the numbers for the codes it is throwing. Good Luck!

 

Ditto