This is about how long I like dyno pulls to be. Shouldnt take forever, just have to load at the beginning to give the turbo a headstart then let the engine rev.

 

I just watched your vid. That's converter slipping. It's coming up against the converter and then riding it till it couples and then increases in rpm. Lock the converter and it should make a cleaner pull. I'm sure you can see this on the dyno graph. If the power isn't falling off, then it's not blowing out spark. 500hp on 10lbs on 4.8 sounds about right to me.

The wg is really big for that setup too. And the big (diameter) JGS spring is the lighter one, 7ish lbs. The small one is about 10. You'll need it and posable both springs, especially in a 60mm gate to get much over 14-15lbs of boost. A 60mm gate has a lot of surface area to be easily pushed open by back pressure and then its a HUGE leak once it's cracked. A 4.8, just doesn't make enough exhaust to make more boost with it open much.