don't know what everone else thinks but i just took my 2.5" catback off and put the stock system back on (i've got 6-3-1 HM stainless headers still on) and i can't notice the power loss at all, its just quieter. i got the catback for $80 second hand and now its on our other vl, but just a thought for those who are planning on exhausts for power gains, they don't really make a difference i don't reckon.
i reckon just advance the timing, cut a bigger hole in the front of the airbox (or CAI if you want), and some top gun max leads. total cost $50, how cheap is that. K&N filters don't do anything really either so there's another $100 to save.