My old 400, I used 1.5'' radiator hose and did not have to rejet using stock exhaust. Also had 27" bi/tri combo with a clutch kit and it pulled them great, they are the wife 400 foreman now and she has no problem turning them. Heres a pix of her bike with a snorkle using radiator hose and pvc pipe.
<a href="http://community.webshots.com/photo/272" target="_blank">http://community.webshots.com/photo/272 ... 6734Jmhusq</a>
<a href="http://community.webshots.com/photo/272" target="_blank">http://community.webshots.com/photo/272 ... 6734Jmhusq</a>