ohh yer forgot about the el bit...

i am out of ideas...
just replace EVRYTING ign wise,

what about the dizzy gear? is that all good?
and the dizzy insides?
rotor cap? leads,plugs?

Compression test

Cap and rotor were replaced when we originally did the cam.

Splitfire plugs and leads were installed at the same time.

So everything ignition has been replaced, bar the coil. That would be next test.

Dizzy gear, no ideas on how good it is. If it had chipped a tooth or something, I'd expect the ignition be all over the place. But its worth the 20 mins to remove and check.

As reported before, tested compression a on second attempt at cam check.

Cylinders 1 to 5 were all around the 150psi mark. Cylinder 6 was 125psi from memory.

Although lower than the other 5, it shouldnt cause that much problems. I can understand if all cylinders were rooted, but just a little more than 10% in 1 cylinder compared to the rest...

I keep getting the idea of a vaccy leak (or something vaccy related) there somewhere - your vacuum you quoted in your first post seemed lower than what it should be, and you've noted that - perhaps compare your vacuum now with what fairmontman's is. I can only think it's something that's been moved/disturbed in the area you've been working (whether vaccy or not), and that is around the head area. The thing that shoots my theory down is that there's not too many hoses to pull - brake booster/PCV(PCV okay ??), etc - I can only see it possibly as a hose off - surely not leaking inlet gaskets, etc. I can't really see any components having failed, although you've got no choice to not check or swap them.
Apologies for stating the obvious I suppose . . . .

Feel free to state the obvious. At the moment, anything is better than nothing. Im appreciative of all the suggestions.

It does sound and feel vaccum related. And the vaccum reading can be affected by many engine factors.

We think we have checked everything that can be vacum related. Checked all vaccum hoses off the intake, they are attached and seem unbroken. Booster hose seems ok as well, unless the booster is rooted. But fairmontman hasnt complained of any brake problems.

Tightened inlet manifold bolts as best as possible. PCV is OK. The valve rattles like it should, which to my understanding means its working. Unless there is something I'm missing in that regard.

I was hoping someone with more dignostic experience with vaccum gauges could point out what a low vaccum reading with a vibrating needle meant.

Could be due to a valve not closing properly. Sounds like its idling the same as my car when i snapped a valve spring and as a result the valve was opened slightly causing a significant drop in compression.

Rapid vibration in vacuum gauge with smoke means worn valve guides.

If the vibration occurs at a higher engine speed it indicates leaking inlet manifold/head gasket,weak valve springs,burned valves or ignition misfire.

I would check the leads first.
Then I would go to the wreckers and get a set of rockers with lifters inside and bolt them on.If the problem persists go f@rt.