Thanks Dave and everyone.
As for the sound... here is a video with the stock manifold, 763 cams and stock turbo exhaust:
And here is one with the new manifold, 101 cams and a 2.5" KO Racing exhaust:
Now I realize the 101 cams make a huge difference but even when I had them installed with the new exhast on the stock manifold, I was still noticing a big drop-off in power above 6500rpms because of the TB and manifold. You can hear on the second video that it no longer sounds like it is struggling up there. Time to see if I can raise the rev limit again.