These numbers were tested on full load. So lets say if im driving with 1bar boost and 3bar fpr on full load fuel gauge should hold 4 bar of fuel pressure ?
Then it seems i am lacking 1+ bar on load
This sounds like you need to give this car a complete checkover, and I'm pretty sure you'll need a fuel pump (upgrade possibly). Also, original pump, how about the fuel filter? probably never changed either, but hey yeah go on and bolt on injectors, turbos etc and go to town on it to make all the powerzzzzzzzzzzzz