As described Au valve train is tapping like mad, been through the woes like everybody else copied and tried countless efforts to no avail.
There seems to be zero clearance on the valve yet it makes that tap sound the worst when fully closed. It does get better when fully open to almost gone but just not quiet as solid as other cylinders in same position.
Stage 4 CMS head and cam profile to my knowledge is fairly new and possibly just run in is there a chance the spring has settled and is now needing more shimming? It's only got 2 factory ford shims when I thought some people would run one factory and one custom shim which is a bit fatter.
Also I think the motor sat around for quite some time before I bought it put it in and started it, is there a chance the spring on that valve/ cylinder has been compressed in that position for extended period of time it's now gone a bit soft?

I would say it doesn't have any preload or enough pre load on that rocker..