The engine runs real rough when I'm going above 55mph on the highway. It runs perfectly under that speed. There's no problem with the front end either.

I've replaced plugs, and wires and it didn't help.

I checked the egr and at idle when I pushed up on the diaphram the engine stumbled some. Then I got the engine warmed up and had someond push the brake and gas at the same time and I didn't feel the diaphram move up.

Does that mean it's bad and is causing my engine to shake on the freeway?

Did I do it right?

 

Don't think that test is adequate. The EGR usually only functions when you are moving. If you think it's operation might be causing your problems, just temporarily cap the vacuum feed at the manifold and take it for a test drive. This won't prove the valve is sealing when not operated, though. If idle MAP/vacuum is good then it probably is sealing ok.