Ryan94transam

Just changed out the intake manifold gaskets on a '94 Z28, and now she shudders pretty bad at 4k rpm's on up. It's like hitting a wall when you get to 4k. While the intake was off, I removed the EGR to see how dirty it was, and it had a lot of carbon chunks just inside the openings. If you shake the valve, it sounds like it is packed full of gravel. This normal?
What else would give problems like this? It feels like it might be surging a little during normal cruise rpm's too. The intake oil leak is fixed, but this is now a new problem. Any help would be appreciated!