When i deflapped and cleaned the inlet manifold on my M57 330d, i definately noticed quite a drop in torque below 1750rpms. But mine is a manual. The flaps were in good condition overall with hardly any chance of breaking up to be ingested (@115k miles) but they were leaking oil all down the side of the block. I changed the EGR Pressure converter at the same time as it had been thumping for years and started to quack. Over 1750 it revs better/harder. It is remapped to 280hp/450ftlbs approx 30k miles ago. DPF still on.
A couple months later, i renewed the red intercooler pipe and gained some back
