I doubt it's a clutching issue, if it was load on it not just rpm clutching would come into play. TPS is a position related thing and is not strickly a rpm thing, I hope you understand what I mean. If the throttle is always in the same position when it acts up it would be suspect. I believe you said the dealer had check that and it's pretty hard to screw that up unless he had a low battery on his tester. I would get a friend over to help and put the nose against the wall, raise the back, pull the air box and start running it. Try adding fuel as you open it up and see if it,s just a fuel feed problem. Also watch the servo and make sure it stays open once you get past 6700 R's. I've seen them open and close again. Keep the belt on and the track spinning, you can put some load on it with the brakes. I had a servo motor go on a 600 once when they first came out with them. I didn't know much about them so it went to a dealer. He worked all day testing it and could not find anything. I borrowed a ecu off another guy, didn't help, then I borrowed a servo put it on and all was right with the world again. The dealers test showed it worked right. Good luck, it's gotta run pretty soon!