I have an 1990 Bonneville SE approximately 200,000KM.

Intermittently engine runs real rough, stalls and or hesitates on acceleration.
Usually cars runs well, Problem is very intermittent.
Has happened with hot & cold engine.

Plugs, wires (used dielectric grease) and Oxygen sensor have been replaced.
Coil was replaced approximately 5-6 years ago, approximately 140k on it.

What do you suggest?

Either a MAF (mass air flow) sensor or a failing computer (ECM). Any Service Engine Soon lights and/or codes?

Yes check for codes first.

No service engine lights, I do not have diagnostic equipment.

Is it best to bring it in and have a diagnosis done on it or try replacing the mass air flow sensor?

what about the crank sensor? maybe its gettin old and cranky.

Thats the great thing about this car. No diagnosis equipment required.

Linky

Coils are notorious on my 1990. You may want to check that first.

My only experience with stalling happened to my 90 SSE. It would just die on the side of the road and would not restart until about 5 min. of trying.
It turned out to be a bad Ign. control module or connector. Once it stalled on the interstate and wouldn't refire. I finally tried unplugging the ICM connector on the side of the highway and put it back on and it fired right up.
Went home and cleaned and tightened all the connector sockets and bought a used ICM at the bone yard and its been running like a champ since.
Your problem could be any of the electrical connectors or sensors intermittenly
failing. One thing to try is do you have spark or injector pulse when it stalled?
Does it immediatly re-start or take a while? Fuel pressure?

Sounds like a problematic Magnavox ignition. I have changed over all of my "C" 3800s to Delco

If you decide to swap a Delco in there (which I would do no matter what, it'* worth it) refer to this thread. It will answer almost any question you've got about it.

I recently did it myself and the difference is unbeleiveable - it was worth it 100%.