Vacuum leak on 91 Ford Explorer

I have a 1991 ford explorer that has a vacuum leak near the rear of the upper and/or lower intake manifold. I cant find the leak and i have replaced many of the hoses and vacuum pipes in the area. The only thing i can figure is one of the intake gaskets may be damages. Has anyone ever had a vacuum leak at a similar or same spot and found the problem, if you have please help me find the fix. Any help is greatly appreciated.

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