Looked at a 95 brougham hearse with an egr valve that is stuck. Valve is located at the back of the intake manifold (looks like a son of a gun to even get the bolts out, or even see them). Valve is stuck open...diaphram is in a position where it would be with constant vacuum applied. Valve has a rod in the center that goes into the intake manifold. Concerned this is where it is frozen/stuck. Wondering if the intake manifold might have to come off to even replace it. Any tech advice would be appreciated.