My neighbor had exact same year Dakota as mine (1993) except his was standard cab with 3.9. I think he told me he was getting only 15 mpg too. Believe I heard others on this thread say the same thing. Doesn't make much sense to me.

 

Interesting.... So essentially just the the lower intake gaskets? my plugs didn't look fouled or anything when I pulled a couple of em but if the plenum has issues with that it couldn't hurt to replace to play it safe.

 

Yeah the guy I got mine from said he got 15 with mixed driving, and my first tank (which was mostly city driving) I got about the same. One thing I know for sure from following a couple TBI builds for chevys is that both chevy and dodge's TBI systems were verrrry temperamental to say the least. I know if you get them absolutely perfect and dialed you can get pretty decent MPG, sometimes even better than EPA numbers but if one thing is wrong the "house of cards" falls over pretty quick. Same with running issues as I am dealing with now haha

 

I did the Hughes Engines kit for my plenum. I have seen other post since that the gasket issue shouldn't be happening because of the alleged different expansion rates of the steel plate plenum and the Aluminum intake barrel. If that is so then the problem may be due to poorly installed gaskets at the factory. Anyway either way just do the gasket, or get a kit which adds in an alum plate and that issue is solved. I had to get one set of longer bolts with the kit, extra. I don't remember if the intake to block bolts needed to be longer too. If you do a kit they should be able to tell you.
I eventually put all new sensors in mine and even at one point just replaced all of the fuses just because it is old.

 

I did the math once upon a time, and the difference in expansion between the two was measured in ten-thousandths of an inch. Different metals ain't the problem, the bolt from the factory are too long, and the gasket compresses over time, then blow out, and leaks.