I don't know the proper term for it. I was coming back from the store on the backroads and on a long uphill I put it at around 4500 in 3rd and for the rest of the trip on uphills and while accelerating it feels like it's skipping on one or more cylinders in spurts. Feels exactly like engine braking except I'm giving it gas instead of letting off.

 

Does the engine do this at all during idle? Do you have any vacuum leaks?

 

it doesn't do it at idle, but it does idle pretty low sometimes.
Don't know how I would check for a vacuum leak

 

For vacuum leak, if you can't hear it, you can feel around all non fluid hoses and see if you feel drafts, especially when reving the motor.

To give you an idea, you can pull the small black hose that goes from your PCV valve to your intake manifold. You will notice the idle goes wonky with the hose pulled, and you can put your thumb over it and feel the amount of suction it has.

Usually, with missing and running problems, the usual starting places is tune up, especially if it's been awhile. Inspect the spark plugs, check the wires via am HEI spark tester, check clean or replace distributor cap and rotor, check ignition timing.

If the plugs don't tell you anything (fouling, etc) and doing a tune up didn't fix it, then you go onto the more expensive ticket items, compression test, leak down test, block test etc.

But ruling out vacuum leaks is a cheap and easy and good thing to search for first. Rule that out, then tune up areas, then bad head block areas.

Since it seems to idle fine, the IACV and FITV probably are okay but I wouldn't rule them out, they are known to get dirty and cause issues too.

Hope this info helps.