Bog
I am fairly confident it is not my reeds. I have had bad reeds a couple times and I am not seeing the other symptoms that I normally see. I am currently running double stacked early M8 reeds with OVS stops.
I have NOT checked my baro tube so I will now. I found some improvement by taking quite a bit of fuel away in the 3,000 and 5,000 numbers (BD RG kit). It improved but did not cure it. As the OP said if I get the sled rolling just a little bit then hammer it it does great, but if I hammer it from a dead stop it falls on it's face for a brief moment then takes off. If I am on the verge of boost it seems to run great but if I am not it falls on it's face. It acts as if it is not getting enough air when not on boost.
My thought in wanting to eliminate the large intercooler is that it is quite restictive. I could see the possibility that when you hit the throttle the engine is not able to suck enough air through the intercooler until the boost starts to come on. Of course I could be completely wrong on this, just trying to come up with some possible cures.
Edited to add that I am running 50/50 110/91 10.5 pounds at 7000-8000 feet.
I have a 2008 M8 Race Gas Boondockers Kit, 13 psi, 8000ft, 3/4 100LL rest 91 pump with the big *** intercooler. It isn't your intercooler, because I've had mine running where it would pull a wheelie out of deep powder from a dead stop even with high 62/58 gears. Now, there always is a tad bit of turbo lag, like a second, but it should hit like a rocket went off once boost builds. Mine started developing a huge bog when I ran into electrical problems and my fuel pressure started fluctuating. You should see a firm 40-42 psi, I run 42. If it shakes back and forth from like 38-42 that won't cut it either. It has to hold 42 or whatever you set it at like a permanent line was drawn on your gauge, at least that is how mine is when it runs good.
Have you replaced your pipe sensor anytime soon? I've heard that when those start to go out they can think you are running too lean, add way too much fuel right off the start, flooding it and cause a bog. There is a thread that tells you where to get Duramax diesel ones for cheap that apparently have the same specs as the Arctic Cat ones, like $30.
Also, when my diamond drive started to go out my sled acted like it had a huge bog, but it was metal shavings in the DD locking it up. I would get stuck all the time, I thought it was tuning trouble because the sled acted like it had no power in deep snow for like the first 5 feet from a stop, then the metal shavings would clear out and it would pick up. Then the DD completely locked up, I punched it and started smoking my belt on a flat trail. I rebuilt my DD and my sled immediately lost the bottom end bog...
What about your power-valves? My brother had a sled and his power valves got stuck wide open for some reason. It had a horrible bog until he figured out what it was...
I've also had baro tube trouble. Same thing, but ran kind of crappy bottom and top, water in the line...
