In particular the bigger looking regulator next to the fuel regulator. It looks like it takes a vacuum line - but what does it do?

What engine is that? The larger diaphragm looks like it pull up a lever on a shaft.

I'm not completely familiar with these engines, but could it be that it's a TVIS like device that opens a set of butterflies in the runners to realise a bigger port at a certain revs? The Toyota 4AGE engines has this on, and it effectively blocks half the intake runner on each intake port, until a certain revs, and then opens up to allow higher air flow at higher revs...

Otherwise a idle control valve of some kind for when the aircon kicks in?

It uses vacume to open the secondry intake butterflys, if you take the manifold off you can see them. They normally are all carboned up, thats why i usally remove the whole sharft and weld up the holes.
I have not noticed any difference in the way they drive.

So I just hook up manifold vacuum to it....when the car is under boost does that shut these butterflies again?

The butterflys are generally used to lengthen or shorten an intake runner to maximize torque from idle (short runner) to midrange / top end (long runner). They are usually rpm triggered with a vacum solonoid.

Do as sssute says. Remove all evidence as turbo vehicles rarely benefit from such a device. Weight reduction is a bonus. You will be able to have a continental brekkie with the weight savings on the car!!

Hehe, yeah they go...but maybe not before first start up.....don't fancy pulling of the intake when it's close to starting....

Found a thread with all the details, apparently it will still run under vacuum alone, just not as well as with all the complicated vacuum tanks and solenoids.

Useful thread on butterflies

I still have them on mine, I have it plumbed up just to manifold pressure and they are a bit dicky.

that thread is useful, that volvo cruise control vacuum pump looks interesting. Can't really see the point for most of our applications though, maybe in a street car.

They were saying they saw more torque until 4800rpm, that might be interesting....as our cars might spend some time down that low.

I'll just do the easy way for now and hook up a vaccy line, then they are open most of the time.

I had the same setup on the old NICS RB20DET in my HR31 skyline. I noticed that the removal of the butterflies made the car an absolute dog to drive off boost. Fitted a ball bearing turbo to make up for it!