After hearing detonation at the top of third my tuner pulled timing. The detonation was lessoned, but still there. I hadn't modified anything since the dyno tune. Even after changing out the fuel filter the detonation remained. I figured it was the cold weather. He strongly suggested to plug off the upper plenum hose and change out the pcv valve. I did so, and now no more detonation? I had been running an oil seperator before.

How much oil in the intake does it take to lower the octane rating? I didn't think I had that much oil ingestion in the intake.

 

It's not going to suck in large amounts from the PCV hose all at once, but it will gradually build up in the sump of the lower intake under normal driving. When you go to WOT the increased air flow will pick up that pooled oil and deliver it to the combustion chamber. Also, the gradual build up of oil can also coat the fins of the intercooler and not allow it to pull heat out of the charge air. Try pulling the intercooler and cleaning it...

Sounds like your seperator wasn't working that well...

 

Yep. It was just one of the cheap air compressor type seperators.