I average about 25MPG where I live, though, it seems to have gone down lately. Not sure why, but I doubt it was the throttle body. My TB has been that way for awhile now. I think the dang tire shop lowered my PSI when they rotated my tires...

 

I own 2 Neons, Great little car. Faster stock than Jap stuff. As a professional mechanic for 35 years I have come to this form and got few good answers. If you are coming here for professional advice you may be in the wrong place, and that’s OK. Just know were you are.
Water leaks in truck and rear floor board. If rubber seals look good , remove and clean inside groove (rubber and metal surfaces both trunk and rear doors) and lay a beed of Silicone inside the groove of the rubber seal and reinstall.
Both neons are starting to idle to low and rough. If you touch the pedal slightly it helps. I plan to look into it soon. Will start with clean throttle body and checking volts on TPS in closed position. Every car is different

 

In my "non-professional" opinion: one could also just go buy new taillight gaskets and replace them. ~$15 IIRC and takes 30 minutes to do. When those gaskets fail on a Neon, that lets water into the trunk, which will run forward into the interior of the car itself due to the design of the car. Unless the weatherstripping around the trunk and rear doors has physically failed due to age or damage, I don't see water getting in around it. The only time I've seen it is when pieces of the weatherstripping were missing.