Dodge Repair: Engine, vacuum lines, running down the highway

Question
Please help. I have an 89 Dodge Dakota with a 3.9L engine. About a week ago I noticed that it would lose power/speed while running down the highway at 55 mph. I thought this was the cruise initially so I free footed it and it would still want to lose power (even going down a hill). There are no engine error codes.

I started investigating it and I noticed that the plugs were fouled (all of them), so I checked the coil and wires and everything seemed fine (I just recently installed a new rotor and cap).

I then did some more road tests and it was apparent that the longer I ran it the worse it got. The first couple of miles it would run perfectly, then it would gradually get worse as things got warmer to the point 45-50 mph was maxing it out. As it gets bad you can smell the unburnt gas. It gets particularly bad going around a corner real slow, the engine is very sluggish and wants to die.

I then decided to take the muffler and cat converter out of the loop and it made no difference.

Then the strange thing is that after one of these road tests I will pull into my drive way and the engine will idle fine and not want to stall if I shift into gear with the brake pressed down.

Thanks, Jason

Answer
What's the history of your oxygen sensor?  Do you have a check engine light on?  Does it work or has someone maybe disabled it?

I would suspect fuel pressure as well but that may be a little overboard at this point since you said you could smell "unbunrt gas" and the plugs were all fouled.  Also, check your map sensor and vacuum lines to it (if not attatched to the throttle body like newer models).
Doug