Should I drive a car with an undiagnosed problem for 1200 miles or throw money at uncertain repairs?

I'm driving an 04 Elantra with 83k miles on it that suddenly developed an acceleration problem last week. The RPMs rise very slowly in every gear and I have to use dramatically more gas to speed up than I used to if I want to hit the speed limit in a timely manner. The check engine light is not on and the car makes no unusual smells/noises. I've had two mechanics look at the car and neither could identify the source of my problem. One suspects it's the clutch and the other was quite confident it isn't the clutch. Some people on the internet have suggested it's the fuel pump and filter. Out of desperation I've used two bottles of fuel injector cleaner, changed the air filter and spark plugs. Nothing has helped. I'm on a road trip in New York and have a great deal of driving left before I get home.