Agreed, I'd be disappointed with that myself. When the new motor was completed, I tossed the Blowzilla onto the new combo, unchanged. It made 3psi on the new motor where it was making 9 psi on the OEM shortblock. I ran that way for a while until I could get back to the tuner and get it dialed in with the new motor. On the dyno, after some tuning and pulley changing, I was putting down a little over 400 HP and somewhere around 460 ft lbs with 9-10 lbs of boost. AFR right around 12.1:1 and do not remember the total timing but I do remember having conversation about the EEC/Tune pulling timing on subsequent runs as everything warmed through.
Fast forward to now. Flowzilla inlet and one size larger pulley (I've accumulated several). At WOT on an average day, I see the boost gauge run just over the line @13 psi. No knocking or pinging, 93 Octane pump gas, OEM style ignition system with a boost a spark, and a nice steady AFR in the very low 12s at full tilt.
The damned thing runs like a raped ape.
On hotter/more humid days, I don't see the boost gauge get as high. It does vary. On a 100* day for instance, I'd probably see 10 psi on the gauge.
I've never had the car/engine dynoed without the blower. It's been on it since day one, so I can't say how much of the entire combo is the direct result of motor or boost.
I think if I dug around, I could probably come up with my build sheet somewhere, if you're interested.