Hello everyone im totally puzzled by this fuelling problem....

When I start my car the fuel pressure is sitting at 4 bar. (Cossie regulator). The car will idle fine for as long as u like. Take the car and give it a hammering then when the car idles again the fuel pressure slowly increases to 5 bar, twitches up to 5.5 bar, then drops back down to 4 bar. Then just keeps doing the same over and over.

Fuels pumps have been replaced twice. Tried 3 different brand new pressure regulators.

Can someone give me some ideas as to what this can be???

Thanks,
Pete