Installed a Big Sucker air cleaner, plus some used Screaming Eagle mufflers, a Vance & Hines Fuelpak, and to top it off I wrapped the pipes with heat wrap from head to mufflers.
It is faster, more powerfull, runs cooler, and as a bonus my fuel milage is better?????? Is it the heatwrap?

 

More like the air flow have checked on a dyno. Mine was get great mileage but was run real lean by two numbers lean. Run great but can run better.

 

Majority of it is more volumetric efficiency of opening up the induction and exhaust systems to run more air through the motor. Always remember, motors are just big air pumps, more air = more fuel and thus power. If you really got a sharp tuner and a good dyno it's amazing how much more performance you can wring out of most motors. There is a cross-over point pushing stock motors however, where w/o beefing up some internals your reliability will suffer. On the other hand though you can use that as an excuse to "go-big" with increased displacement which drags you into another whole tuning regime. It's a slippery slope once you start, "speed costs money, how fast d'ya wanna go?"