What's the elevation you were at? If it's high elevation, the normally aspirated engine will be lacking in power compared to at lower elevations (less air means less fuel burned and less power).
It doesn't sound to me like it's likely to be a fuel problem (though I could well be wrong). I would check the air filter first and the exhaust system for constrictions or plugging second. It would also not hurt and not be hard to inspect the air inlet piping for obstructions or unusual constrictions. Apparently at least some versions of the air deflector (on the Ford chassis) have a sort of flap that can get out of place where the tube to the air cleaner hooks into the diverter thingy on top of the grille.
It's not unusual for the floor to get fairly warm between the seats, as there are exhaust components--and the transmission--right underneath there. This is particularly true under load at relatively slow speeds (at high speeds, there's more airflow to move the heat away). It's also annoyingly normal for the vents to blow quite warm air, especially after being parked for a brief time, since the engine is right under the dashboard and vent ducts.
(Note: I'm generally assuming a Ford E-series chassis; some details may be different for others.)
