That APC solenoid is expensive. I've had two fail, but both times failed to base boost. Not uncommon for it to fail to WOT. Might be worth a quick swap with your buddys valve. Maybe a five minute job.
On another note I've had problems with SQR ECU's. Three tries now and it's still not right. First try was a stage III and the second two on custom guesstimate Stage IV+. Can't really fault them for the stage IV's since the have never seen the car. Everyone makes mistakes, try and find if you have hardware failures.