When I bought my supposed rebuilt engine I was told it had Kenny detweiler ported heads and intake. I got it disassembled and inspected and just like all the other BA claims it doesn't appear to be the case. How much horsepower are a set of Port matched heads and factory intake capable of supporting without pushing them to the limit with really high boost?
Those heads and intake will more than support that 67mm your runnning.
How much boost is really a mythical answer
Depends on many factors
Compression
Backpressure and the list can go on and on.
The turbo is really the key to power throughout the curve
And running a journal bearing turbo will not get you the torque you say your looking for unless you have a healthy amount of compression in the motor or have an undersized turbo for your combo.
These motors don't have alot of rpm capability so the window is small to get the turbo to move the air.
Most don't know it but it's easy to hit Backpressure on a small ex housing and old set of compressor/ turbine wheel combos. Even with poor a wastegate strategy.
So their boost number will always be higher in the attempt to make power and will choke out powerwise.
When Backpressure is low that's when you see the higher power levels with less boost if your setup can do it.
In the end you would need a very good turbo and system along with a motor built with better ve in place to make power with lower boost.
I would highly recommend you run those heads and intake and start working /building a setup around that