The pipe that is on this engine has a removeable aluminum "choke" in it. Maybe I could ask the pipe builder for a larger choke to see if that fixes it. Afterall I am riding between 800'-1300'. Although when I had the sled in Valemount BC it would happen on long WOT runs uphill at 6500' or so.
yep...higher altutude on long run full throttle...I bet it is to tight of a stinger...get a bigger "choke for it" and I bet it fixes it..if you throw the stock pipe on does it run perfect?