again, it's hard to say, but knowing the rep of Accords ... I'm still going with the EGR valve. (The EGR stands for Exhaust Gas Recirculation. Exhaust gas is routed back into the combustion chamber because the exhausted air is much hotter than the intake air. By sending warmer gas into the combustion chamber, the air/fuel mix does not have to do as much work to heat up, and your engine runs more efficiently.)

It has 2 positions, closed and open.

It's "closed" when the car is at normal driving speeds. (0 to 55)
It's "open" when the car is at highway driving speeds.

I'm guessing it is clogged, and is stuck in the "open" position. You're constanly cycling exhaust into your engine, thus bogging and killing it.