Trinity Racing has their Stage IV exhaust coming out for the YFZ. I was in there the other day and they were testing their pipe and it gained 10hp on the top with at least 5hp on the rest of the power curve. This was done at the end of the day and they were not even able to get the correct jetting done. This was also done with stock timing and the airbox lid on. I know it is coming out a little late, but the dyno had a bad bearing and Trinity Racing wanted acurate results. Look for their upcoming results on the finished pipe and their Project YFZ. It will have a ported head, cam mod, 13:1 JE piston, lid removed, and Trinity Racing exhaust. Trinity Racing has been building the Z400's to beat and plan to continue so on the YFZ. Go to www.trinityracing.com or call them at 877-FASTOYS.