quote:and the ideal idle jet setting will result in the highest intake manifold vacuum as well.
George, may I add..
My experience with marine engines is that setting the air screws to highest vacuum (in neutral) produces a pronounced dull spot right off idle, its a very lean state of tune that provides low torque and finiky behavior off-idle, often many overcompensate by wildly adjusting the accel pump system.
A manual trans car is the hardest to set these screws best...with an autotrans, highest vacuum in neutral shows a dramatic drop in idle speed when finally put in gear, demonstrating the low-torque tune. Opening the throttle takes the fuel droplets out of suspension faster than the accel pump can recover...then a dull spot off-idle results. Settting the screws for strongest idle (and even best vacuum) in gear provides enough load on the engine to now set the idle mix such that the difference in rpm in and out of gear is quite minimal, often less than 100 rpm and off-idle throttle response is dramatically better.
In boats I set these air screws idling in gear vs neutral. The result is no-throttle starting when warmed up, and the boat leaps out of the hole instead of stumbling or having to feather the the throttle to overcome an off-idle bog. The end user is usually quite happy with the results.
Naturally, its hard to load a your manual trans car similarly. The typical end difference in the air screw is 1/4-1/2 turn in from the highest vacuum position (no load), a slightly richer condition than the typical highest-vacuum condition.
So, my point is try a slightly richer idle condition than you may have now, you may be happy with the results.