Well, depends, you could get away with adding new pipes and just doing a stage one jet kit. but really there are a ton of options. I guess a lot of peeps usually just do both in conjunction to get an overall power increase. I have modified pipes and have not changed my air cleaner yet, but my 1800 is fuel injected. will be changing soon the air cleaner and adding the pc usb III, and maybe changing out the pipes for a set of HK3'S. anyways that's my two cents.