Air/ fuel tuning

ap6street said
im assuming here because the lean spike is from a high speed cruise , you dont get a full pump shot and therefore more relying on the powervalve to enrich the quick change ???

Yes and no. Correct that generally there is less pump shot the more the more the thottles open. How much less depends on the shape of the pump cam. The pump shot is needed to cover the slowness of the idle circuit in responding to changes in throttle. Its not needed so much, or at all, when most of the fuel is coming out of the boosters. (If the main circuits are not responsive enough, the pink cam is one that can be used - but it gives up low opening movement to do so.)
The Power Valve is different. It stays open as long as the manifold vacuum is low. In your case, when the manifold vacuum drops below 6.5"Hg, the valve will open. This allows more fuel into the main circuit.

also you said the powervalve restrictions? is this related to the amount of extra fuel the powervalve allows through?

Exactly. These are like another set of jets in the main circuit. They control the amount of enrichment.

would a drop in the secondaries be a good idea?

I wouldn't touch them until you're done with the primaries.

and yes i do enjoy trialling things back and forth especially if i got a bit of an idea of whats going on , but just want to know the limits of lean mixture before i do damage

At light throttle, the engine will miss or die if its too lean. The danger to the engine is when its at or near full throttle. Don't test the lean limits for that. For full throttle, just make small changes around that 12.8 it ran good at on the dyno. Test at the track to see if richer or leaner it makes faster and test richer first. I'd be cautious if its much leaner than 13.2 at WOT. and of course check the spark plugs for any evidence of problems.