[las27563481]

The first thing i would look at is the air filter - again. Did you use the K&N cleaning solution? I'd go through that again, clear the code and see what happens. I can't see it being the 93 octane fuel, everyone here has been running that with nothing but good results, some here have even mixed with E85 (myself included, 1/3 ratio - bone stock car) with no issues and better performance/response. I'm not saying the E85 mix is the fix, just saying more octane is hardly ever a problem, other than expense, possible overkill.

System too rich is not looking at octane, just at fuel to air mixture with stoichiometric of 14.7:1 being ideal, dependent on engine load. On most scanners you can see this looking at real time data over OBDII. If you can, maybe remove the filter and compare #'s with and without the filter temporarily.