Gooood LATE afternoon, welcome to JustAnswer!. This is Ed.
Check the EGR tube interface to the upper intake manifold. The lip seal that seals the EGR tube from the outside world often becomes torn or mis-shapen upon reassembly of the intake manifold, resulting in a vacuum leak. In the old days, a vacuum leak was accompanied by a lean engine misfire, but this type of fuel management system simply compensates for additional air entry, adding fuel to match. That means the engine idle will be higher and codes will be set.
Find the EGR transfer tube and wrap your hand around it. If it's leaking as badly as I imagine, you'll feel a vacuum pull on your skin.
The leak may be at the EGR valve itself if you didn't replace the small fiber gasket that seals between the valve body and the tube. They're not very tolerant of motion on the tube, which crushes the fibers in the gasket and allows extra outside air entry.
And then...there's the seal between your upper intake plenum and lower manifold. If a rubber plenum seal happened to slip out, it will hold the intake up and allow extra air entry to the entire engine. An individual misfire code may be set, but this is a pretty smart system and may be able to compensate for an uneven amount of air charge. Shooting some carb or throttle body/ brake cleaner spray under the intake area will tell you if there's a leak because it will cause an immediate change.... either good or bad. Change is bad in this case.