My wife's car stumbles sputters surges and losses a lot of speed and power when going up hill or when pushing hard on pedal to accelerate pass someone on freeway. Thought it was a dirty fuel pump so I replaced the fuel filter (in tank, fun!) and fuel pump. It helped a lot but the problem is still there. Does anyone have an idea of what it could be? I'm thinking fuel pressure regulator. I will replace spark plugs next but car has 100k miles and was told it could be ign. coils problem, MAP, Purge control vulve, acceleration sender, clutch sensor, etc. All I know is, if this car was anything like my 56 Chevy it would have been fixed alreadly.

Thanks, Bobby