I'm kind of asking this for a friend but he doesn't know it yet. If you had a 2009 Touring model and had every intention of eventually doing a full Stage I but had to do it one piece at a time for whatever reason, which would you do first. The TFI is already a foregone conclusion so I'm just asking about the air cleaner and some slip ons. Keep in mind that slip ons are going to run anywhere from 3 to 6 times more $$$ than the air cleaner portion and money is a part of the problem. If you just did the TFI and a better air cleaner to initially save money, would you notice much of a performance increase? Or do you need to do the entire Stage I to really see a difference? Thanks for everyone's input!