It's also important to note that Drive Pressures are not constant throughout as people seem to be indicating.
At 20#s boost I'm 1:2 (i.e. 10# drive pressure to 20# boost). At 40#s boost I'm 1:1. At 55#s boost I'm 2:1.3 which is less ideal but a good compromise as I spend little time at boost pressures that high.
DP is a compromise. The lower the DP the less parasitic loss and the more hp but the slower the turbo responds which can be a real problem on the street.
You are also attempting to control where on the compressor map you are operating. For instance if you are overspooling your particular turbo a looser turbine housing will definitely make more hp. On the other hand if your boost is low and response is poor you might gain a bit by going tighter on the turbine housing just because you can now stay on top of the charger.
Good Luck!
