1994 Volvo 850

Engine problem
1994 Volvo 850 6 cyl Two Wheel Drive Automatic 140000 miles

when I push the gas hard the car start to surge but a vacume plug on the right side of the intake manifold blows out, then I have a huge vacume leak there is also a small line off this plug ( looks like a freeze plug with a small line out) the line runs under the fuel rail. This seems to be way too much pressure for the intake side.
can you help. Where do I start checking?
January 27, 2008.

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