89 Caprice still funky

Even though it will rev up when in N or P, it does not take the same amount of gas as it would if you tried to rev it to the same rpm under load. So you rev it up test doesn't really prove anything about whether it's getting enough fuel when you drive it.

-- Elbridge Gerry, of Massachusetts:

"What, sir, is the use of militia? It is to prevent the establishment of a standing army, the bane of liberty. . . Whenever Government means to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise a standing army upon its ruins." -- Debate, U.S. House of Representatives, August 17, 1789

Does the check engine light come on ?

That's a good question because if it does not then it points to a problem in the secondary ignition like the wires. I don't think an 89 Chevy will set a code for that. OBDII certainly would, but this precedes that.

I have a 91 Caprice that had similar problems. After couple months, I replaced the gas tank cap. No more problems. I suggest you do the same.