i have run my predator on the dyno ,achieved 47.88 hp with k/n and w/b slip on,with stock filter and w/b achieved 48.22 ,so rejetted up to a 155 and the k/n w/b pipe made 49.19 , and the stock air filter w/b with 155 jet 47.94 so for the pipe only the stock jetting will do but add the k/n and you will lose hp ,unless you add some jetting 155 works the best at sea level, this is all rear wheel hp all hp @8050 rpms