65 170 vacuum advance or not?

All he did was advance the initial timing. The 400 can easily stand around 20* initial because it has very low compression. Leaving the vacuum advance disconnected is a very dumb thing to do, especially on a street driven car.

It will drastically reduce part throttle response and the fuel mileage will suffer. The operation of the vacuum advance is to pull the timing up at cruise speed to help burn some of the extra fuel out of the cylinders and aid in pert throttle response.

He masked it being disconnected by pulling the extra timing in. Thing is, you can do both, as long as the vacuum advance can is plugged into a ported vacuum outlet.

You should check the initial timing where it is now. Then plug the vacuum can back into a ported vacuum source. It will run fine.

The fact that it is running better since he disconnected it is not because he disconnected it. It is because he pulled in a lot of extra initial timing.