[94Blk5.0]

If there is gas on a plugs, you might have a sticking injector somewhere. Run some injector cleaner through your next tank of gas, as mentioed in above posts.

Gas guages have nothing to do with figuring MPG. All you need is a correct odometer, and an accurate gas pump.

Is there a chance the coil pack is not providing enough spark energy? I doubt it, but worth a look.

The MAF and the O2 senorare the primary senors that provide input for A/F ratio, I think, but you have new ones , so those should be good.

Is the thermostat working right? Runing too cold can cause rich conditons.