Quoting slugsgomoo:
I'd switch to the non projected plugs as well. BR7ES might actually help you a bit.
Frankly at that boost level, even if your wideband is reading pretty happy AFR, I think your timing is way aggressive. Unfortunately your only timing control is w/ base setting so you can't do a lot but i'd drop down to 3-4* base and see if you get the same behavior.
Thanks for that info Andrew. I've been looking at the BR7ES plugs and will give those a shot. They seem to hold up better in higher boost settings. I'm still debating whether or not I should just set the base timing to 5* or lower. I just don't have all the tools to do the timing so I'd rather do it once. What's the disadvantage to retarding it more than I should (say I could have gotten away with using 4* but I decided to run 3*)?
Edit: forget the last bit. I'm going to start at 5* and keep checking to see if I'm getting knock. If I get no knock at 5* I'll turn the boost up. If I see knock, I'll lower the timing to 4* and try again. Long process but it'll work.