I recently added a flowmaster dual exhaust system(cat back, no new headers), i think it was the 40 series muffler, and a k and n high flow air filter, my friend swears my truck is faster, but i haven't noticed much of a difference. I have the 5.4 V8 on a 2001, my guess is this adds a few hp, but does anyone have a rough guess of how many i would have gained? Also, i heard i might gain a few more hp back if i cleaned my Mass Airflow sensor, is this true?
Any help would be awesome!
Alex

 

The prospective is this. You can't feel a seat of the pants power increases of very much less than 10 hp.
These mods don't approch that much most of the time because you most likely have lost some low end torque with some small gain near top rpm where you don't run most of the time.
I'm sure you will hear a different opinion but you already see this has happened.

 

Yeah, i kinda figured thats what would happen, but hey, i think my mpg has gone up. BTW, i took the truck mudding today and it handled like a champ, stock tires and everything, had to pull i guy out, so i guess that low end tork might have helped a little