after a great deal of effort, we have FINALLY got our 73 450sl to run. now we are trying to take care of the small things. we still have a rough idle and in searching the forum for possible answers i happened on the vacuum thread with diagrams of our system. i noticed that there is an item that we do not have on our system. it is located between the throttle housing and distributor and is called a 2-way valve in one place i read and called a switchover valve in another. our system just has a white plastic tube with rubber ends from the throttle housing to the distributor. does anyone have an actual picture of this item and its location under the hood? the rough idle seems to be reduced when the engine is at operating temp. so i am wondering if this could be the problem. we have replaced most of the old rubber components (fuellines/vacuum hoses/etc). we do not have any info regarding this car from past owners as it was purchased at auction. and it appears as thou someone had been trying to correct some sort of problem in past by by-passing a few things that we now have sorted out. any suggestions or pics would be of great help.