I have a 93 300d and it has been working great and yesterday i started it and it started fine ,thirty seconds later it quit. I notice the smoke when it started to die was black , I had my sister start it while i was looking under the hood, I saw that the valve on the turbo intake side was getting a vaccuum and closing off which choked out the motor ,i opened it manually and the car ran fine .I traced the vaccuum line to a small valve with an electrical plug on the top of it ,is this a solonoid and what is it suppose to do when it works properly. Could it be this simple just replace it with a new one .thanks