are you sure you want to mod an eight year old sled?
power inc. used to make the yamaha gyt pipes so they would be a good chioce, or check with bender racing to see if they still have something. you could put boyesen carbon power reeds from a yz 250 (they don't sell enuf in carbon to package them for that sled). be sure and get clutching specs if not a complete kit set up for that set of pipes!
HHHM, my thoughts are $$for pipes+$for reeds+$for clutching+$$from sale of 94 vmax = newer sled that is as fast as a 94 vmax with pipes & has better supension(& probably more reliable)