I've never worked on FEs before my current 427 but from 4 to 12 cylinders even race engines I've always found vaccum to be an advantage.
Some says there's no difference between vaccum and not, particularly on track cars. I challenge this especially on powerful engines - when driver maintains engine mid-range during a curve before the throttle gets hit WOT for the straight. The well timed ignition system - so vaccumed in our case will have more linear response ensuring a progressive power curve thus better times
Once we tested same track same driver with and without vaccum.
Driver thought his times were better without, it was actually the opposite.
No vaccum compensated advance will increase the feeling of kick in the bottom thus make the driver believe it's more powerful. Don't be fooled
