65 170 vacuum advance or not?

So I noticed something on my 73 Charger 400-4bbl when the mechanic came to my house to adjust timing and carb. He disconnected the vacuum advance and left it disconnected. It made a world of difference in how the car drives and performs. There was no hesitation and you could floor it without it stalling. He tuned the carb and adjusted the timing on my 65 170 but didn't leave the vacuum advance unhooked like on my Charger. Would it make any difference to disconnect it on my 170? It doesn't have power brakes or anything else. What does it do to change the way the engine performs? He checked my carb on the 65 170 and he said there's nothing wrong with it. He did say it would need some valve stem seals possibly because of the smoking. I think it may need a cylinder head rebuild. Because there's no telling how many years it sat before I got it.