if the rpm is different at the same speed then it is definitely the clutch. Another reason the power might be down is oil. After such a long trip the oil loses viscousity thus the motor loses a bit of compression making it feel like you have to push the gas a little more to do the same thing. also you will get that tapping sound from the valves if the motor oil gets too thin. Also I've noticed although honda recommends 5W30 which I found is not thick enough. Most honda owners I've talk to burn a little oil when using 5W30. When I switched to 10W30 I had no oil burn. Which is definitely better if your using an expensive synthetic oil.