2002 Grand Caravan misses when warm but coughs on the freeway

My 2002 Caravan develops a miss once warmed
and up drives fine on highway/freeway but above
40-45 mph when i try to accelerate and especially
on a long uphill grade it pops/backfires through
the throttle body and does not accelerate well at
all.
Work done: Transmission rebuilt 500 miles ago,
thoroughly cleaned throttle body and toss (they
were filthy), new champion plugs, replaced wires,
coil pack, new plenum gaskets, new air fuel filter, 3
cans seafoam, checked wiring to fuel injectors for
melted wires, checked for vacuum leaks. Seems to
run a bit worse when heater is on (checked
alternator ~13.6v output. I'm getting a raw gas
smell when it backfiring from throttle body.  
Haven't load  tested battery, but starts fine. I don't
know where to go from here.