Yes, we had the 260 out all afternoon for several hours, running between 2/3 and WOT. I got lucky on this go around, new plugs didn't fix it outright but... Your advice was on the money. I think I had mild condensation in the cylinders over the winter which thankfully was corrected with the fogger, the regular fuel with ethanol deteriorated over winter and the Heet added alcohol back into the gas, and with 8 gallons of new gas and injector cleaner it started and finally after about 5 minutes at 2/3 throttle it started to run more an more smoothly as the new plugs, fuel, and fogger did their magic. It began to get it's "soul" back. Then it began running like the beast it is. I genuinely appreciate your post. I know this was simple in the end, but I had bad feelings early on since I had to have a complete BRP crate engine replacement 3 years ago under the extended warranty, under almost identical circumstances. Funny thing is the engine failed without a definitive diagnosis from the dealer or BRP. All maintenance was dealer performed prior to the failure.
To anyone who buys a new high performance BRP ski I recommend the extended 3 year warranty. It paid for itself with my engine replacement. And yes, we ride it like we stole it, after all that's what it was made to do!!