basically the tube you want to sell us is 3'' ID, stock is what 2.75''? so it would be bigger aka more air. however the TB will still be the same size 2.75. so gains will likely be minimal. also you would probably want to have an AFC and do a tune when you installed this as the MAF will be reading the wrong amount of air. in theory assuming you can stuff more air pass the TB with this larger piping the car would then run lean as there is more air but less fuel. now the cars do run slightly rich from the factory but i'd rather run rich then lean any day. especially when i don't know how much leaner i would be. also afaik there are no TBs that are 3'' for our cars which again makes one question the gains...
anyone please correct me if i'm wrong in anything i said above...
op: if i were you i'd make a 3'' place racing style intake and sell it as a whole unit, pipe, filter, etc, as its the best after market intake for our cars. i think you would get more business...and try to find someone to make 3'' ID TBs for us...
edit: most people who buy this will need a new filter unless they can cram there old one on. and even if their old one did fit many would like to just have a clean new filter instead of recharging there old one(if that is an option) or going out to find a new one to fit the new pipe. Also if there want to sel their old intake it having a filter certainly makes it more likely to be quickly sold as it's a whole unit. i think you should offer an optional filter with the kit, i'd offer both a a K&N and a cheapo alternative. mark em both up 10 bucks for the fact i don't have to drive to buy one and you'd have a sale...then again my apexi is just fine
. then again intakes are 95% sound, 5% performance...