Hi All,
Just purchased my high miler (as per sig) and was alarmed to discover a horrible vibrating/rasping noise when the engine was cold. Only present when on the gas and seemingly worse as the revs rise but not audible after about 3k. No noise when idling. Goes away once warm. The dump valve sounded a bit strangled until then as well....

Well contacted the previous owner and he sad has been like that since he owned the car for the past 10k and the noise is from the dump valve while cold. (HKS Seq Dump Valve).

A couple of Qs.
1) What would cause this?
2) Is there any way to strip and clean the dump valve (cost over £200 new).
3) Is there any danger that the dump valve is sticking and may cause some kind of damage when cold?

TIA

Cheers