Munich:

TomGuy is right that cleanliness is an advantage which will help to rule out "Sticktion" as a cause of your trouble.

With respect to vacuum and FI engines, there is no venturi as such in an FI engine, just a throttle plate where vacuum signals exist just below the plate but are highly variable because the opening and closing of the throttle valve. The most reliable vacuum signals are straight from the manifold and in fact this is the primary source for the V8s where it is tucked away at the back of the engine near the firewall, not at the throttle plate where it varies. The vacuum advance is taken below the throttle plate, for what reason I cannot say, but it seems to not affect how the engine runs.

Based on what you have indicated it seems that your M130 distributor operates like the one on the M117 V8 in my 350SL. The vacuum cannister retards the spark a fixed amount until a certain speed is reached, a temperature is exceeded, or the AC comes on and then the three-way valve cuts the vacuum so the centrifugal advance operates unrestrained to give the engine a bit more advance. The amount of the vacuum retard can be quickly determined by setting your timing by the book with vacuum connected and then watching the mark as you disconnect and reconnect the vacuum line.

I like the way my V8 runs w/o vacuum so I simply plug the line to the distributor and my engine operates great. It's not sophisticated at all but very effective. You might want to crank in a tad more advance in little bits, 1-2 degrees at a time if possible until you feel you've extracted all the performance you can.

To answer the question you raised, yes you can hook directly from the manifold, but then you lose the ability of the "system" to cycle the vacuum on and off according to those variables listed above. You'll probably be happier with no vacuum line to the distributor. As a side thought, any chance you can latch on to a euro-style distributor for this engine? It may make a world of difference in your satisfaction.

For what it's worth...

230/8