I've looked at Wallace Performance in Aberdeen as they do tuning thats different from Courtenay and Refal (EDS) and there website says this (Which seems alot different to what Courtenay and Regal say):
Our new Z20LET kit is designed to give a faster, more aggressive response from very low down in the rev range. Unlike other manufacturers beliefs, the standard Z20LET is only good for a power figure of 235BHP. This is given by manufacturers spec and the turbo is working at 100% it's maximum load capabilites. If more power is desired the turbo charger has to be changed.
The standard intercooler is a very good design and gives a low pressure drop with a good decrease in temperature. Changing this intercooler for a larger one with smaller end tanks will result in a higher pressure drop, defeating the purpose of changing the intercooler.
We are looking into a more efficient intercooler based on the standard design. Also with our EVO235 kit we have changed the throttle positioning to respond exactly to the user's input. Before this when the throttle was at 30-40% the signal passed to the throttle butterfly was 80%+!! This gave a feeling of a powerful car but when you put your foot further to the ground nothing happens!! Now, the car responds how you want it to. We have modified the Traction control to give a more aggressive start.
In their advert in it mentions 235bhp MAX because of small exhaust housing or summet...
Yet Courtenay and Regal can do over 235bhp without changing the Turbo...
Who's telling the truth?