hey quick question, is the oil filler plug the bolt that is to the far right in this picture? Some original photos have not been recovered yet.

yeah im pretty sure it is. but it has been a while since i had a look at one of these. i think it kinda looks like a small dipstick when you take it out.

Just to clarify, a BOV is unsuitable as a bypass valve, why? Would it not work in a similar fashion to a wastegate, provided a suitable soft spring was fitted instead of the normal heavy boost type and the boost pressure was not applied to the base of the piston valve. Manifold vaccum at idle would overcome the spring pressure and open the valve. As the throttle is opened low vaccum in the manifold lets the spring close the valve and when manifold pressure goes positive it would re-enforce the spring closing. Is the limitation simply the small "diaphram area" relative the the pistion/valve area. Would not reversing the normal air flow direction and a soft spring, as suggested above, overcome this problem.