downpipe question

[04PontiacGTP]

I just got my exhaust system done, 3 inch downpipe no cat and magnaflow 2.5 catback no resonators. My question is since im running no cats shouldnt my check engine light come on? Ive been driving for a couple days thinking it would eventually come on but no lights. Any of you guys experience this? Or I was thinking the previous owner could have swapped the ecu out.

[Bio248]

your SES will be on most likely unless your car is running stupid efficient.

[TheOtherNick]

It really comes down to drive cycles, most days you will not preform a whole drive cycle and the test will not run so the light will not come one, after you do a longer trip with mixed driving the light will come one.

[Slick2500]

Mine came on after 5 min.

[04PontiacGTP]

I ask because the car had an intake on it and just bolt in mufflers when i bought it. I'm thinking maybe they put it back to stock when they gave it to me. Im curious if they had an actual ecu upgrade on the car now since my light has not come on in a couple days.