..i'd stay with the stock airbox...unless you want to get into a bunch of head-aches..these s9s gotta good strong engine without screwing around with the air..
..stadiumyamaha.com for oem parts..
..i got that belt from scootertronics.com ....i've had some good and very bad experiences there..should be alright just getting the belt, tho...
..you can roll fine with oem clutch springs ,they effect take-off timing mostly.. but i do suggest getting a 1500 main counter-balance spring..some call it a contra..torque spring..
..and for you to comfortably get top end speed, you MUST HAVE a unrestricted set of driven pulleys..cant really run the 743-20-30 belt with restricted pulleys..it'll cause the belt to over-ride the variator and drive face...
..and dude..dont sweat the questions......it's why we all here..we all have so many to ask...
peace