I bet you'll have no problems w/14 psi. And isn't nice to know you can put a higher boost pulley on, dump some high octane race gas in, and make lots of extra power?
As far as Supras & 91 octane, they don't get along. I have not dyno'd my car on 91, but on 92 it made low 380's (this is prior to the big intercooler, which would help). It makes mid 450's on 100 octane unleaded, which is all I've used for several years now, since the car isn't my daily driver. There is way too much exhaust backpressure from the small stock turbos and manifold, and the boost levels I run push the compressor out of the range where it's efficient.
The key to making good horsepower on low octane gas is to increase volumetric efficiency. For a small engine like mine this means keeping peak cylinder pressures and thus peak torque low, but maintaining that level of torque over an extended RPM band. Since HP = TQ x RPM/5252, you can see that a small torque number can make big power if it can be maintained into high RPM's.
I think low 500's would be the most I would shoot for on 91 octane. You could get more, but popping the motor by being too cheap to buy good gas would be kinda stupid.
You 03 guys have a big advantage by being able to spread your cylinder pressures out over 4.6L and 8 cylinders. Much more pump gas friendly than a Supra on stock turbos.
