Gas does sound likely. Try one of those over the counter gas additives,
most are pure alcohol, they mix with the water and get burned along with the
gas. I have an 03 that ran better after spraying some fuel injector cleaner
in the intake ( is was stalling but not due to the gas ) One more thing is
double check that the gas cap is on tight.

Local newspaper had an article retailers who use additives in thier gas
"Toptier.com"  as a list of retailers who add detergents to thier gas.

its not the gas nor the gas cap as been suggested.

Well...it happened again last night... 45 miles from the house at
midnight....only this time it continued to...lose power(like the automatic
tranny was in neutral)...it would run for a little....lose power...coast to
a stop....had to turn off engine...put in neutral/park...restart...finally
limped it home(took 2 1/2 hrs!)...repeated the "trip" drive this morning
taking it to the Kia dealership....they pulled the codes...slippage in the
4th whatever/torque converter issue...New tranny time! Thankfully the tranny
is still under warranty(this was the SECOND!!! tranny that the Kia dealer
has put into this car)...Tranny only has 10k on it... We're carless for 5
days(no trannys in stock)...Has anyone else had this car problem??? What do
we need to be on the watch for now???:-((((((((((((  :-)Liz