Great comparison info Imaj with the dyno! I take it you don't have the GM tune? I do and am interested in how that goes. Vince says he can do great things with it too.
It will be great to see what you can do above the westers tune.
Anything at or above 300 rwhp will be a watershed moment for the car. Stock bolt ons = +300 rwhp = 
Actually 300whp has been done with just bolt ons, the sky here at the shop did over 400 ft/lbs of torque and 300hp at the wheels. The GXP we used for some development hit 295hp and 345 ft/lbs with stock turbo, stock downpipe and stock cat at only 21psi. That was the car that we tested the intercooler, intake, charge tubes and tunes on, her only other mod was a magnaflow exhaust. The real limiting factor seems to be the exhaust side of the turbine, that is a tiny little exhaust to be flowing those kind of horsepower numbers through, at some point you just can not push anymore exhaust through the turbo, you can run more pressure to help push it out, but everyone is so far off of the stock compressor map already, that at what point do you stop? The more pressure you push at this point, the lower the adiabatic efficiency you are seeing, which means you are heating the air more, which ultimately starts reducing power at the wheels, causing detonation, and other bad things.
I have attached a picture of the stock compressor map with some common pressures on it and air flow references, as you can see most of us are way off the map already, so it will be interesting to see how far that little turbo will go before the compressor blows apart, and or we just create so much heat that the gains in pressure are offset by the extra heat in the intake charge.
Also there are some assumptions made in this graph for atmospheric pressure, humidity, etc.
One thing to notice on the graph is how well the turbo works for the stock setup pushing 15ish PSI and 260 horsepower, it really puts the turbo in a real sweet spot for sure, and even the GM upgrade at 290 still keeps it on the map pretty well even at up to 23 psi. This is an example of a correctly sized turbo for the application, but it can only go so far.
Then for comparison this is a compressor map of the big compressor wheel that we have here, and as far as we can tell is the same compressor wheel that other vendors are using in their upgrades also.
The other big thing to consider on this, the ECM is looking for a certain air load, not a particular pressure. That is why you see varying pressures depending on what altitude you are at, and probably the reason we saw some guys go into limp mode at the dragon. As you go up in altitude, for the engine to hit the target air load it has to spin the turbine faster and run higher pressure, so if you have a tune that is already pushing 22-23 psi and you go up a couple thousand feet, it may need to push an extra 1-2psi. Which on most tunes without the beta fix from HP or Westers will cause you to go into limp mode after a few seconds. So if you tune the engine for 27psi at sea level, and you decide to go up in the mountains to play, you could start hitting 28-29psi. At some point the turbo can't be pushed to higher and higher pressures without thinking about the long term effects on the compressor or turbine.
In the end the biggest thing to be concerned with is airflow not pressure, as air mass with the right amount of fuel and a spark is what makes power. Try to get the air to flow through the
system the best possible and you make more power at lower pressure
good luck though and let us know how it turns out!
Thanks,
Dave
