Spark Plug Analysis help - Low boost under load

So these are Bosch Tri-Electrode Copper Plugs, Heat Range 6, were not contaminated at all before I put them in. Did maybe 1 hour of driving, a good amount of stop and go at first and this is their condition. First plug on left was sightly oily, but the rest were black and sooty just around the surface gap; tips OK. A/F on narrow band read slightly rich under load.

I just re-installed the head after having it resurfaced/valve job/lifters/seals after I noticed oil in the combustion chamber, apparently induced from heat damage. The car had not been able to hold boost under load and it would sometimes stall when coming to a stop. I don't see any oil in the chambers anymore and the car didn't stall once which is great, but still having trouble holding boost under load.

Where should I look next? Different plugs? Based off of the cars history here are some possible culprits
- Fuel pressure regulator could be bad, it's the original (91) and may be time to upgrade to an adjustable one
- Possibly restricted Cat converter - it's been through some rough times while trying to get the tuning just right
- Noticed a pinch in the lower wastegate line, fixed this - havent tested yet
- TPS Calibration is good and throttle cable adjustment is good

Any direction is much appreciated. Thanks!