If you do a mod to an engine...ANY MOD, I don't care what it is....and it forces you to open up the needle from where it was before the mod......congratulations, you have just done something to increase horsepower.

If you are tuning the pipe length in small increments and gaining rpm with each cut, the engine will tell you it needs more fuel. I anticipate the need for more fuel by opening up the needle before the next start up. This is a must for true speed engines with a very high fuel demand.