At the end i instaled fuel filter with 6BAR FPR.
Firs problem is that B7 fuel filter have 10 mm return valve hode, and B6 have 8 mm. So there is need to done some modifications. I use ruber hose to make that transtalion.
I started the car, and everthing was alright, then I try selveral times to squize return hose with my fingers, to check is there any pressure in it. That was a huge mistake, becuse after i have sqiuzed the hose, my fuel pump start to make noise. It is still working but it make noise
To numbers
At idle i have 6.0 bar on fuel rail, testing at 13.2V and injectors full open, pressure drop to 5 bar
Fuel pump compust about 7 Apms
Do I recommend anyone to do this? NO... It is far more better idea to get bigger injectors. It is safer and at end it cost less
I am lucky beacuse i run my car on LPG, when I run on petrol, pump make noise and it is only a mather of time when it will fail. Not more safe car to drive on long trip
Here is a log with origianl 4 bar fpr vs 6 bar fpr