If the '04 only need 2 size larger jets, why did you guys jump so far up (11 sizes)? You are now up 7 sizes and I will bet the engine is too rich and this is probably your problem. I would suspect the the engine will tolerate the big jets at high speed but at a high vacuum setting (part throttle) it is way too rich and the engine loads up and stumbles. If I were you I would try 3 or 4 sizes up from stock and check the plugs to see what the mixture is where the problem is occuring. BTW, before those nitwits at HMF released the pipe for sale for the '05 they should have done some jetting tests so they know what's needed. Very poor way to do business.

 

We jumped up that far cuz we opened up the intake too. I'll try to get some time here in the next few days to do some plug tests n stuff. I really haven't opened it up and looked since when I havent been riding, I have been very busy with other things.

It probably isn't HMF's fault, they never officially released it for the 05, I talked to my mechanic and he told me the 04/05 pipe was the same.

 

Even with the intake mod, 4 sizes should cover you. But 7 is probably close to twice what you need. Look at you plugs, they will tell what the mixture is doing and how it need to be adjusted.