I know you don't want to hear this, but for real, check out your clutching/deflection, even if you think it was ok a while ago. My sled got worse and worse over two years of mild riding, with me chasing the oil pump return, plugs, wondering about the map, etc. I ended up noticing that it was pretty boggy just crawling along slow, and checked where the belt was riding on the secondary... Way too low. Thus when the engine tried to engage the clutch, the gearing was too tall, which was evidently pulling the RPM's down, and that would for whatever reason cause it to just die. (No gurgling, if I stayed in the throttle, it would die just like I hit the kill switch, or like the throttle safety was not contacting. If I released the throttle it would idle.)
Setting the belt to ride higher in the secondary has completely eliminated the bog. Or it was gone on all of last year's rides anyway... I'm off to West Yellowstone next week, so we'll see how it likes that!
I'm not real familar with what you've done to the clutches, but if deflection checks out, you might try a good clutch cleaning too. ??
Chris