Lid and cold air intake,
The Flowpac is certainly one of the latter IMO.
Some people will claim it's great, but in general these are the people who have bought it and a) need to justify it or b) have no experience with any other setups.
I'd get a lid - any lid, they all perform the same. Although TSP and SLP appear to have the best writeups concerning fitment and quality. MTI and Whisper are alternatives.
Filter - The stock OEM paper filter is fine for 500bhp n/a. A k&N isn't bad, but you'll see no HP gain with. Plus cotton weave filters like k&N's are expensive to maintain (cleaning solution and oil), more so than just buying a new paper one. Plus when dirty (which happens quickly with k&n's) they generally perform worse than paper filters.
Smooth bellows is a total waste of money and does NOTHING. there are even theories which would claim it flows worse than the stock one. Although still not by enough to show up on the dyno or at the track. Save your money. If you must there is the "gernco" mod which costs like $8 or simply buy a section of 3x3" humped silicon tubing for $15 instead of the $50 that SLP charge. BTW - SLP's one is just a bit of 3x3 silcon tubing anyhow.
So for the same gain just lid and new paper filter will be as good.
If you want a CAI setup then it is generally accepted that the FTRA (Fast Toys Ram Air) is superior and has shown much better results consistantly at the track.
lid + paper filter + FTRA = cheaper and better than SLP Flow Pac




