Help! Dakota Turbo owners!

Has anyone with a Dakota turbo had problems getting the aircraft to smooth idle and also idle shutoff without it lumbering on for minutes? Now this is not due to any of the common troubleshooting problems. I have had the manifold valve, metering unit, and fuel pump overhauled. I've had two reputable shops confirm proper operation of these components. I also installed a new Marlin Waste gate. New GAMI injectors, properly installed (problem existed before GAMIs). Upper deck leak checked. Rigging double and triple checked. Hits the ICO stop.

Spoke with tech rep from Continental who suggested the Manifold valve drain may be connected to the common drain line. That was not the case. But it is connected in common with the fuel pump drain which I have been told could be a problem. Continental says Manifold valve relief drain should be a dedicated drain. We are checking that next week when the fuel pump returns from inspection. Also my A/P is going to check all cylinder drains for obstruction. He has already checked the drain's 2 way sniffle valve for operation.

Any other ideas out there? I have been down now for almost three months. BTW, the aircraft otherwise flys great and matches up with all power settings.

Thanks. Chris