Bringing up the revs takes the engine out of the idle mode. Sounds like your idle air control valve (IAC) is dirty. I have had the same problem on my 1990 740.

It's not hard to clean even if you are not a mechanic (I am certainly not!). Go to http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#Cold_Start_Dies_Dirty_IAC. This is part of the amazing 700/900 FAQ compendium developed by Brickboard supporters.

The IAC is located underneath the wheel that guides the throttle cable. To release the electrical clip on the IAC, push the thin, U-shaped wire down into the connector to release. If I had know this the first time, I would have saved half an hour! Be sure to use fuel injector cleaner, not carburetor cleaner, as the latter (supposedly) can harm teflon or other non-metalic parts within the fuel delivery system. Use surgical gloves on your hands when using the cleaner and stay upwind as the stuff is toxic. When the idle air control valve unit is in your hand, open the valve itself with something relatively soft, like a popsicle stick. Don't use a screwdriver, as you don't want to create scratches.

I did this two years ago for the first time and it took a while. I did it two weeks ago and it took less than 30 minutes, hood up to hood down. Obviously, once you get this fixed, you'll need to look at the PCV system and other related components, but these can wait a bit. Best wishes on your investment!