Assorted engine running issues

[Guest OB6D]

Howdy peoples,

When my engine is idle it revs itself. The revs go up down, up down, up down with about 200 rmp. It makes me nervous. At the traffic lights it's like i'm one of those dudes that's constantly playing with the throttle.

It used to smooth out when i would squueze the bypass for fast idle shut, but that don't help anymore.

The engine is also not to eager to run above 4000 rpm.

I've heard a sort of backfire rumble in my exhaust, these poof, poof, poof, sounds on release of the throttle.

Performance i guess is fair, maybe sporty, but it don't feel like 180HP to me nor 160.

I installed on of those Equus turbo gauges, the one with the pressure hose attached to it. On that it makes 0.4 bar boost pressure at most. That's manifold pressure.

I've checked throttle body microswitches, with an ohms meter and filler gauges, or how do you call those things. Anyways that should be okay.

My air mass meter was sticky, but i've cleaned it and it's now okay. Also tested ohms according to manual, the thing seems okay to me.

Because the engine is in the back of a Matra Murena, i've placed the intercooler above the gearbox at the side of the cylinderhead with a blower on it. The air lines then also had to be custom build. The inner diameter of my self made connections are larger then that of the original aluminum stuff. Also the distances between the connection points have therefor slightly increased. Dono if that has effect. Bit more lag i guess...

It always starts easy. Response to the throttle, is smooth. It doesn't stall or anything. It revs like baby i'm ready to go, but then falls back into this annoying i'm going slightly mad idle.

Maybe it's worthy to add that it feels to me like all power is under the first half stroke of the gas pedal and that pushing it deeper seems to make barely any diff...