Would shortening the stock pipes/muffler on a 82 yamaha 400 have a significant affect on performance if any? please help if you can, because when i had the pipes separated(on the bottom where they connect) there was a big decrease in performance...not sure if shortening would make it worse,i need to shorten them because they hit the axle(3 wheeler axle on rear) and rub on the tires.PLEASE HELP