I translated tis from the C20let forum it seems as though arno has been playint with some kind of low back pressure turbo to up power output he might have started ripping his MK1 chasis apart with all the extra power ( I think) and the bottom line is that it just costs too much read for your selfMoin!
The Phase-5 will probably never give it in this form, is simply too large the expenditure (financial)!
It was times an experiment to drive with a counter-pressure-reduced turbocharger the achievement upward still further but for the moment the project, the intercooler is located in the cadet burst, all welding seams must be revised, if the car runs again and the outside temperatures again are durably cool gehts as a check times on the role!
We have the last Ph-4 measurement with completely out-squeezed load pressure (1,7 bar) in May made, there came the following with raus:
Phase-4 with 1.7 bar load pressure