pffft. Anyone ever calculated the actual difference in compression between the NA heads and the turbo heads?
The difference is minimal, and on a 9.0:1 NA engine, the turbo head will drop you to around 8.7:1. The turbo head flows a bit better, so you can expect a bit more top end (only sightly less pathetic) and possibly a little less torque everywhere else.
On the other hand, an NA head on a turbo engine will get you from 8.0:1 to 8.3:1. That alone won't make the difference between running 20psi and 12 psi. Simply not true. Heck, I milled my NA head, and was running probably 9.5:1 compression and still getting away with 12-14 psi of boost. lol.
Most of the difference in compression is from the dished pistons of the turbo engine.