Blazin' Bob,
Put away the axe! You cannot solve any problems on that 1997 van by chopping things up. The computer is so well integrated into the system that it would be more work to try to do without it than to just get things working properly. Most of the time it isn't the computer's fault. They regularly last hundreds of thousands of miles. Chances are that "rebuilt" computer you get at Autozone is used and has been checked for function and put in the box with an AZ sticker on it. Nothing was done to "rebuild" it besides checking function.

That kind of mileage around town is typical. Last year I took a 400 mile trip in a 3/4 ton Ram 2500 4x4 truck and it was mostly highway driving. Truck had approximately 40K miles on it and has been maintained very well. Fuel mileage for the trip was 13.5mpg. I was shocked. I began to understand why people say Dodges eat gas. That truck would be hard pressed to get 11mpg around town.

On a 100K+ vehicle it is not uncommon for the O2 sensors to have started to drift. You won't get a CEL but they are not optimum. They don't cost too much from Rockauto. You can get both from Rockauto for less than $70. I prefer NTK, then Delphi. I have heard (three most dangerous words) that NTK are preferred over Bosch. Delphi is the most high tech of American brands, even though they are GM. I am buying NTK whenever possible.

I'd suggest checking the individual plugs and plug leads using the clamp-on timing light method. Look for any traces of missing flashes. That will give you an indication of a problem. I suppose if you were really serious your friend could chain the van to an immovable object and you could run the test with the vehicle in gear with torque converter at stall speed. This is obviously unsafe and so I am not recommending it to you. I guess a chassis dyno would be the equivalent.

360view's information is worth rereading.

Last point, getting the injectors cleaned and flow matched can't hurt although it feels expensive. One mismatched injector could throw off the whole fuel computation system.