Idle control 520i 84 Australian modifications

[Adam]

Any one has details of idle control for the Australian modified BMW with all the pollution control stuff on it. It seems to be a balance of airflows all over the place. I have little control over the idle.
There is a small tube connected to intake Manifold (starboard side) that joins to a larger hose (this larger hose runs between the valve cover (so it basically is the space inside the engine) and the other (port) side of the intake Manifold, there it joins just in front of the throttle valve (it joins where two hoses running water from the cooling system connect to the carburettor, what that does I don't know, I am guessing it is either a thermal shut off valve or a heat exchange, who knows?) anyway, if I pinch the small tube the engine will die, so I figure this is adding to much air bypassing the throttle. So I air is getting in from one side of the larger hose. I disconnected it from the carburettor side and blocked it with my hand with the engine running, it has quite a strong vacuum and the engine produced a very loud valve clunking noises, like I cut off oil to all the rockers etc (possibly not a good idea). Is air supposed to flow so freely through this? What is the water jacket thing for?
The other thing is when you back off the accelerator and coast the car, slight downhill, it will start to “bunny hop” and it is not a good feeling, like it is starved of fuel or air (I don’t know which), quite nerve racking.
So help. Thanks

[johnmpls]