Changed both knock sensors today. The back one is a SOB but I'm persistent. Took it for a scanning run, and there is absolutely no improvement in KR. I'm getting up to 3.5* KR at WOT under 6 to 7 psi boost. The good news is with the BCS replaced I'm getting up to 9.5 psi boost.

I'm running 93 octane. I have tried 3 different types of gas over the last 6 weeks or so, all with the same results.

As mentioned, I replaced both knock sensors. No improvements.

Any suggestions as to where to go next? Could I be running lean? Should I check fuel trims?

Does your scanner allow for averages on the cells for LTFT? If so, post what you have. the best way to find out of your lean is to have a wide band O2. Pull your plugs and look at them, how do they look? Check out your motor/trans mounts, look real close for any shinny metal, that would indicate rubbing and that will set off a knock sensor. Check the exhaust for any contact on metal. Can you hear any add sounds in the engine? Have you upgraded your PCM yet to a performance tune? This can help. A good shift kit has proven to help reduce KR by shifting faster and reducing tranny noise. I've noticed that 2000+ do seem to run a little on the lean side.