I have a Flowmaster 50 dual in, single out exhaust installed on my 5.7 MGM. I didn't see any improvement in HP but did gain a bit in MPG. I got my K&N CAI earlier this week and installed it. I noticed an immediate difference in performance. I can't speak to how much (if any significant) HP gain, but the difference in torque and shifting smoothness through the gears was significant. Also, I could immediately hear how much better it was breathing by the extreme change in audible tone of the exhaust. Much louder and deeper throaty sound. As far as MPG change, its still too early to tell, but the truck is currently reading 15.9 with all light to light city driving. I can't speak to the TRD CAI, but I have always ran K&N my vehicles and never been disappointed.