Hi there

I have a M110 Euro engine. It'svery difficult to tune. The vacuum in the manifold seems low. I get pops from backfiring. The air plate often begins to flutter in conjunction with the engine suddenly running faster at idle. I checked for leaks. Fuel pressure seems OK. The engine has had some valve work. The PSI in the cylinders is around 125. One is little lower at 110.

Is this abnormally low and potentially causing the intake vacuum problem, please ??