its a bitch huh? that happened to me for the longest time, i couldnt even floor the gas pedal. What ended up being the problem is i had a wrinkle in my head gasket and i had oil leaking. i know you said you dont have that problem, but thats what was wrong with mine, sh*t sucks. my baby hesitates now when shes cold, maybe if you let her warm up a little...
hope this helps some,
Isaac