I have a 1994 Park Avenue Buick that has been hesitating when I accelerate, the cruisecontrol works when the car is finally up and running but it wastes excessive gas(far more than it used to). I have to done the following to remedy these problems: changed the spark plugs, spark plug wires, changed the air cleaner, and fuel filter.

None of these have worked, any advice on what else might work?

 

Your catalytic converter is probably plugged. I had the same problem a couple months ago.

 

Believe it or not a tired battery can affect your gas MPG.
Also a lazy oxygen sensor(s) that stays on rich too long.
Of course there are the usual considerations ie., tires low on pressure, hi speed driving, etc.
The last post concerning the converter can also cause a low power complaint. If this is the case , The best way to confirm this would be to do an exhaust restriction test. That's when the )2 sensor is removed and the exhaust back pressure is measured with a restriction gauge and that should not be more than 1-2 lbs. Don't even think of trying to run without the converter. It would be like opening a can of worms.

 

I'm going for cat or oxygen. Oxygen only send a code when they completely go. I have them on my list of things I need to eventually do. The sensors are way cheaper than my Subaru. The front o2 was fried from a bad tune and it ran $150.