84 Riviera won't idle

I have a 1984 Riviera 307 with a Rochester 4bbl. Rebuilt two carbs, new plugs, wires, battery, cap, rotor. It idles rough and generally runs poorly. exhaust sounds like it might be backed up, could be a plugged
cat? any feedback and other ideas appreciated.
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More likely a vacuum leak some where or the egr not seating.

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