i would check the cats. If they are plugged it will cause a mis and run rough. No power. Need to do a back pressure test or just drop the pipe at the manifold and see if air will blow through it easily. I had similiar problem while crusing about 95mph then it just went south. Ran rough no power sounded like missing. Also the MAF will cause similiar problem also. Sometimes you can bang on them and make the fail.