There are a LOT of misconceptions bandied about vacuum advance, which stems from the fact it is generally so poorly understood, even by those who should probably know better.

It might be considered "low performance" by some from the standpoint that drag racing application distributors don't even include it. Performance engines aren't driven on the street, these engines are intended to operate exclusively at wide open throttle, consequently the vacuum advance mechanism itself is simply another potential failure point. Since it isn't ever going to be operational, it isn't needed, therefore it isn't used. See the difference?

But vacuum advance has nothing to do with inhibiting or retarding performance as such, because there is no affect at all if it is working correctly i.e. no diaphragm leaks, advance plate sticking etc. Another source of confusion is the terminology itself. "Total Timing" numbers often discussed, does not include vacuum advance. Sounds strange, but it's true.

For street driving, part throttle operation, and cruising on flat ground especially, there is no practical way to achieve the optimum necessary ignition timing advance with mechanical centrifugal weights and springs alone. That's why vacuum advance was invented in the first place. The proper "curve" is not possible.

Estimates vary, though there is somewhere around a 3 to 4 hwy mpg economy loss without it. Engines have better all around driveability and run significantly cooler. I found my Y likes about 52° BTDC cruising. Now this isn't an exact figure because it is measured in the garage, in neutral, with no load on the engine. Vacuum advance is inherently a load operated device. So far though, I've been unable to find anyone willing to sit in the engine bay with a timing light to check it out on the highway at speed.

The Shop Manual shows somewhere around 45° BTDC - total + vacuum advance using a distributor machine if everything is added up - keep in mind OEM numbers are always listed in distributor degrees - not crankshaft degrees - and most Ys had an initial timing of only 3° or 6°.

Short answer: "Yes you want vacuum advance". Nod your head yes.