Jim is very correct. Put a compression gauge on it and start there. After that, if everything was good, I would replace every piece of vacuum hose you can get to.

Beyond that, I would also consider a valve and timing adjustment along with the other tune-up things like maybe an O2 sensor.

The thermal idle control valve under the intake on the right side of the engine might also be suspect if it is leaking or sticking a bit.

Good luck,
Michael