[madmaxmenon]

Hi all, i'm sure this has been covered before but I could not find a thread for it. I am looking to build a track bike and wanted to know what are the must have mods. I am looking to go racing on the cheap and hence the 250.
What I have in mind so far:
brake pads (suggestions?), steel braided lines and fairings.
Planning to get the woodcraft rear sets and clipons. They don't mention about gp-shift though. Leo vince full system and dynojet kit.
Do I gain much by changing the air filter?
What about chain and sprockets? I have heard of 515 sprockets for the 250, anyone use it? Is the stock gearing good enough? If I go -1 in the rear, do I lose a lot of initial grunt? Is it a huge gain over stock at the top end?

Cheers!
Menon