New X1 owner with mod questions!

I just purchased a used X1 and after working on it for a week and cleaning it up i have it running and im ready for some mods. I installed a velocity stack and a ufo open air filter. I would like to change the carb and pipe. I would like to know what works the best and what is the easiest to tune. I also wanted to see if anyone suggests putting a fuel filter on.

Thanks a ton,
Customizer333