Ticking/Knocking Engine noise 1989 Coachmen E250

How long did it sit before you got it? I've seen a lot of cars over the years bog down and not want to go very fast. A few things it could be are;

Mice building a nest in the tail pipe plugging it up.

Internally rusted muffler

Slipped timing chain from miles. They usually last about 120,000 miles but a lot of idlingcan shorten that.

Hook a vacuum guage to the intake and see what you get. A healthy engine will pull between 17 and 20 inches of vacuum.

Now, the ticking could be a sticky lifter.