Just been looking at the vacuum hoses on my 2.8 30 valve and they seem a bit brittle with the fabric flaking off them. I notice as well that one of them operates a valve on the front of the inlet manifold. What does this do? Reason i ask is mine has a stutter at low revs up to about 2500rpm ( see my other post) and was wondering if this valve is not opening properly causing the stutter. Thanks.