Vacuum Advance

For best performance in any mode, all engines require the peak cylinder pressure to occur at a specific place in the rotation of the crank. All your ignition timing systems are designed to hit that target as often as possible.The more time the engine spends at that specific point, the more average torque it will produce, and at Part Throttle, the less fuel it will take to do whatever work you are asking it to do.
So yes, this opens the door to steady-state fuel-economy. But there is so much more to it.

Does your street engine need it?
IMO, absolutely yes.
Here is just one example;
Start your engine and warm it up. Then without regard to reading the timing, just advance it until the rpm no longer rises. This is near to the perfect amount of idle-timing the engine wants. Now read it. Don't be surprised to see 25/30 to even 35 degrees.
Not many engines with distributors can be tuned for whatever you read there. Nor would you want to, especially with a manual trans nor with a lo-stall TC, because the power pulses are just too strong, and the rest of the timing curve is just too hard to achieve. With a manual trans, it becomes very hard to drive the car at low rpm as the pulses hammer the gear-train. With a hi-stall, you can sorta get away with it.
If your T-slot synchronization is pretty accurate, you can retard the timing at idle to as little as 5*, even with the 292/292/108 cam. Well OK, I have done it and with good results.
Put your timing back, lol.