my 550's are maxed out at 18 psi

[Shane@DBPerformance]

Your high throttle settings on the AFC should be -18% at the richest with the 550s. With it at 0%, it would fuel it just like 450s and the duty cycles should be quite high. You should at the very least, remove the lower honeycomb from the 1G MAF. It could still hit overrun, but at least that would be a start. If it starts overruning with the lower out, then you need to do some hacking, or switch to a different MAF. Having the BTDC at 0 would have helped your pump gas tuning and made it less likely to knock.