Hello Brickboard

A few weeks ago, i set out to fix a non-existant idle on my 1987 760 turbo.
I replaced the Idle Air Control and it started running again, but it was idling too high. I then cleaned out the IAC with carb cleaner, and the idle came down, but now is settling at maybe 600rpms. I adjusted the idle screw, but that only covers the underlying problem.

I've also replaced the spark plugs, the "j" hose that connects to the turbo from the air filter box, and re-secured the mounting for the power steering pump (which was a bit loose and i thought was causing SOME kind of problem, at least with the timing belt).

As of now, the car is still idling too low, albeit alleviated by the idle screw, it emits a white smoke from the tail pipe at start up, and makes a rough chugging sound when it's driving.

It may be important to say that today after securing the PS pump and test driving it for a few minutes, the white smoke was more plentiful and, when i opened the hood, was coming off the turbo. This could be nothing more than a few chemicals i had sprayed in a bolt hole on the PS pump to clear out some gunk that had built up so i could fit the bolt.

Needless to say, this has been a very frustrating problem. Can anyone help me out? Any suggestions will be helpful.

Thanks,
Zac