Looking for help diagnosing Bog

So I have picked up an intermittent WOT bog this season, that I have never had. The sled is a 2011 Pro RMK 800 with BD turbo, and has been turboed from '11. I upgraded to Intercooled, TPSmart EBC, and Tial in 2012, and have run the same numbers since then, with excellent results. Since nothing has changed, I don't feel like this should be a fuel number issue. The bog occurs only some of the time, and seems to come and go. When it happens, it is during one of 2 instances. 1) WOT, let off, and then back to WOT. The sled runs clean to WOT, but after let off momentarily and then back to WOT, it bogs hard, and will not clean up. 2) Same circumstances as before, varying throttle and then up to WOT. Sleds hits full boost and target RPM for a second or two, and then bogs hard and falls flat.

This only happens under load (deep snow, uphill, etc.), never on trail or hard pack. I have also noticed that my PTO side plug looks almost fouled, whereas Mag side looks clean and good. Only other thing, is the stock EGT sensor, is throwing a "Voltage Too High" code. I've had this before (different ProRMK), and it didn't affect anything performance wise. Not sure if this could mess with something on a turbo sled? I've got a new sensor on order.
My thought are, Bad Coil or plug wire?, Exhaust Valve?, Voltage Regulator/Capacitor? Bad Aux Injector blowing open at WOT?

Anyone have a similar issue, or have any suggestions? Only code thrown is the EGT probe. Thanks for any help or ideas in pinpointing the issue.

I did change the fuel filter this season. As far as the exhaust valve, I was thinking about that too, but haven't had any time this week yet to wrench. Definitely going to check that out though.