Great results! You/your builder did everything "right".
- Garrett turbo (you never mentioned which one? I presume GT35R or GT40R) and no KKK stuff
- EFI and no CIS
- Carrera intake and not sub-optimal CIS intake
- Bigger IC
- Twin plugs
- JE pistons.
- Correctly sized injectors from scratch
Also, depending on where you take your boost reading from, you might get higher results before intercooler compared to plenum. Your intercooler might be a bit too small. I guess that your internal boost gauge is fed off the brake-booster line and that dyno papers used MAP-sensor, right?
AFR curve is conservative, with rich readings where V/E is supposed to be high. It would be informative to see VE table from your EFI. I believe you could pick some extra torque in the area where AFR's are low by leaning them a tad but it all depends on VE at that revs. If car is breathing "well" where AFR's are in 10's then Pat Williams probably kept it rich to keep it safe which is a sign of a pro. It's better to have a bullet-proof engine with slightly less torque at lower revs than one with hole in a piston