I agree with keeping the vacuum advance. Can't hurt anything leaving it on. Slightly off topic. Years ago I had a 70 bug. It had a 1641 CC engine (87MM pistons) Dual port head, a Zenith 32NDIX carb, mild cam and a Bosch 010 mechanical distributer. I noticed I had to drive it slightly aggressive to get better gas milage. If I took it easy, it would noticeably drop. I realized when I drove it easy, keeping the RPM down by shifting to the next gear, the timing wasn't coming in and hurting the economy!