I have learned that all gas is not the same, I seem so be a sucker for high octane and would fill up at a certain gas station whome would have 94 octane. When I fill up at this place, my fuel air ratio is all over the place and lean. If I fill up at any other place with 92 octane, my fuel air ratio is bang on to where it should be. I run 5-7Pds. of boost at any given time unless I go to the mountains.
Mabee try a different gas than your usual. I know we all have our favourite places to buy gas, but what is good for our sleds sometimes takes residence.