hi all, I've been kindly lent a supersound exhaust to keep my yamaha sr250 on the road this summer. I have it all mounted and set. I took it for a test run and I think it is running lean. The bike will sometimes feel like it doesn't fire (its not awful but its not good). I'm guessing this is lean, too much air, not enough fuel? My question is, is there anything I can do that is not major modifications to restrict the air flow so I can have this bike on the road until I decide on a muffler and K&N filter and then I'll rejet the carb or pay someone to do it. Maybe packing out the muffler? Or is there some carb adjustment I can perform without having to buy a new needle? (the only reason I dont want to do this is because its a temporary fix). Not sure if any of my ideas would work or if there is a better one, but please share some ideas and help if you can. Thank you very much James.