Rough Idle...... on 1999 Nissan Altima

My car idles rough. I'm suspected a vacuum leak and I am pretty certain that's the cause. My problem is I can't seem to locate it. I spray Brake cleaner around the throttle body and it smooths out. I've inspected all hoses and all appear to be in great shape. Any common problems reported on this vehicle? Or do you have any suggestions? Also no codes.

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1 answer
intake manifold gasket is very common.

Roy