How long for ECM to recognize cat back exhaust?

Silver ice 6.2 · February 23, 2016

Well, for example, if I added a "cold air intake" that was advertised as a 20hp gain, a cat back for 10hp, headers for 20 hp and can't forget the famous throttle body spacers for 15 hp, that would bring my 355hp 5.3 up 65hp, to 420hp, and it should get me about 5 mpg better mileage, according to the sellers of these products.

did you really put a tbs on your truck?

MikeNH · February 23, 2016

The gains with exhausts and intakes are almost always way high up in the RPM range and more often than not come at a cost of low RPM power. I've put exhausts on everything I've owned because I like the sound but I don't expect anything else from it.