If you haven't done it yet, see if the injectors respond to cleaning. Add a high quality injector cleaner to the fuel tank. Also clean the throttle body. Doing an on the car intake manifold cleaning would not hurt either.
There are two posibilities in my mind. One is that there is still a slight ignition problem. About the only thing that hasn't been tried is the ignition coil pack. Usually when they fail you will have a constant miss, not an intermittant one. If you can find someone that has a know good coil pack try swapping it and see what happens. The other idea on my mind is that you have a slight lean condition under that exact load and thus the need for the injector and induction system maintenance from the first paragraph. This could have been agrivated from a better functioning EGR system.
I don't know, but these are posibilities worth checking.
