Hello All. A further update on my progress. As suggested by Tomguy, I re-measured the vacuum - this time *between* the valve check for the central locking, and the manifold (about 8 inches from the manifold, at the end of a black rubber hose, where this disconnects from the valve check).

I started the engine, and measured the vacuum at a steady -11" Hg.

I increased the rpm to 2000, and held it there for about 4 minutes (until the engine had reached operating temperature). During this time the vacuum steadily increased to -18.5" Hg. The vacuum needle at this stage was steady.

I reduced the revs to idle (approx. 800 rpm). The vacuum fell to -14" Hg and the needle showed a slow oscillation around the -14" mark (I would say about +/- 0.25" Hg). The idle is not smooth (I am not sure how to describe it, but it is "lumpy", it seems to stumble a little; the rpm drop momentarily, then pick up again - forgive me if I cannot use the correct description here).

I then took a propane torch, and (without lighting it) let propane flow around the injectors and the intake manifold, and along the MAP line and sensor. I was listening for a change in rpm, which I did not detect. But I must confess that I was a little nervous with this technique, and was not as thorough as I perhaps should have been.

I hope to get the cylinder compression tested in the next ten days or so, and a friend has offered to loan me a timing light in the next couple of days. So more information should be available soon.

If the manifold vacuum reaches better than -18" Hg at 2000 rpm, is this to spec, and if so, does this mean that there are no major vacuum leaks? Does the lower vacuum at idle point to another problem?

As always, I will be grateful for any guidance you might offer.

Joe