So, I have looked everywhere online and cannot find a single company that makes velocity stacks for the F4i. Anyone know of a company that makes them? Also, can anyone shed some light on what advancing (or retarding) the ignition will do, and if its worth the $60 for an adjustable ignition rotor?

 

If you want to play with ignition, get a PC3r. It's made for when you have modified your camshaft.

I believe HRC makes v-stacks for F4i. Or possibly Erion.