I have a 1995 e34 euro 520iT 5sp M50TUB20 engine which when very warm idles rough. Once I am at speed its fine and at start up in the morning. Say I get off autobahn for gas - come to stop - then it idles rough and have to really gas it to power through the engine shudder/bucking.

Fault code said O2 sensor which was changed as well as new plugs and fuel filter, but problem now seems worse.

I am thinking its a vacuum leak or the the Idle Control Valve located under airbox. i see posted this site issues with the Mass Air Sensor. Not a mechanic with limited tools and I am inclined to change out all vacuum lines I can reach or any cheap/simple sensors/valves.

Any suggestions or vacuum line diagrams would be greatly appreciated. Thanks Joe

TO see if there is a vac leak the quickest and cheapest way is buy a can of break cleaner and with the engine running at idle spray it over the vac tubes and vanos slowly to see if there is a change in engine sound if so you have found the leak,be carful not to spray it on the exhaust for obvious reasons.
my prob was the maf sensor