Volvo 480 Club Europe

To explain it a bit better, when I get into the boost area, around 0.4bar, the car starts stuttering in all gears and then accelerates normal ish- boost jumps to 1 bar, in 1 and 2 gear. 3 gear the stuttering is so violent that I am too afraid to continue pressing the pedal.
My ECU has the roboumod, and o have just reset it and tried again with the same results.

I have checked the spark plugs, they seem a bit lean,
Recenty I have changed the fuel pump for a warlboro 255lph pump, but until yesterday the car was driving normally with it installed.

I have played with the maf a long time ago, that could be a problem, but I'm suspecting a stuck Westgate or a faulty boost controlel.

If anyone has any idea help would be appriciated

When the stuttering starts, does the boost remain constant or does it continue to increase?

Have you checked for air leaks in the inlet / dump valves?

Welp, i am not sure what was the exact fix, but I suspect it was the Maf sensor. It was held down by zip-ties and they must have lost their strength. Now I made 2 metal brackets to hold in place and after that no issues were notes, a part form similar stuttering when I was low on gas today.

But for anyone else, it happens when fully on the throttle and holding it there, it kept jerking the car as if you were jabbing the brakes with your left foot. The boost was 0.4 0.5 bar when the stuttering was happening, and after it finished with that it boosted to 1bar.