01 800 Cutting out in the mid range

I have an 01 800 summit x highmark with 17.5 pilots, air screw at 1.5 turns, main jets 500 pto 490 mag, and needles are 9zly2 needle set second position from the top. I ride between 6000 and 9000 feet in southeast Idaho. The problem is the sled when ran at about 1/3 to 1/2 throttle and held steady it cuts in and out when the dpm is connected/funtioning. When I unplug the temp. sensor or put the bowl vent straight to atmspheric pressure it runs like a $100. It also works the same when I come off the throttle pitching me into the handle bars or throwing me off the sled especially if I am sidehilling. I tried raising the needle but the sled the seems fat and that happens at the needle setting all the way on the bottom full rich. I thought I found the problem when I found a seal leak on the PTO side of my engine so I hadn the crank rebuilt and rechecked for the leak. The previous owner said it ran great. He put new pistions and rings but didn't rebuild bottom end so that is why I had it done. The way I leaked checked was spraying around the shaft, crank halves, carb boots and cylinder bases and no change in rpm was noted. Where as before bottom end rebuild it would change when spraying the pto shaft. I was wondering if I went with 510 main oem aftermarket jets or different needles. The needles I would need help on a choose ie what number. If I am over looking something please help. I am willing to do the full blown engine leak test if I have to or are the new oistions just sucking fuel and air so good I just need the right air/fuel ratio in the mid range. Is there anyone that has any ideas please

update to progress

Had the mpem recalibrated and checked by dealer. He said that the mpem took the recal just fine it had the right cal codes in it but he reflashed it anyway. I also checked my reeds they looked ok someone thought they might be a problem as they are the v-force 3 reed if anyone has had issues with these type of reeds let me know.