Bad tank of gas maybe?
I noticed a difference in where I purchased my 93 octane. Chevron was great and I didn't have any issues, 7-11, citgo, marathon, not so much. I notice even in my high compression daily driver 240z, I have to run a quality 93 octane (like Chevron) where a lesser quality 93 fuel gives me the pings.
You could try adding 2-3 gallons of race fuel to the mix (not the octane booster crap), just to see if it makes a difference, if it does, then you'll just have to back out some more timing if you want to run those boost levels on pump...