Thanks for the extra info Jeremy much appreciated!
So interesting that you're running yellow spring and 20W50 weight oil. Looks like I've been chasing my tail there, given your experience and given my own experience - it hasn't changed my lean out issue at all!
You're running HP Performance superchargers - that's what I'm running, the 1050. So when I get the needle details for you that might cut out some of your tuning headaches to get you in the ballpark. It's a 1310cc 9psi max boost, with head and valve mods.
So an update, fresh in from the shed...here's the range of travel that the damper piston had on the damper rod.
vs
I couldn't find an appropriate washer in a quick drop in to supercheap, so I took your advice and used rivets
Drilled out and shaved down to ensure no rubbing on the walls to score them (though the rivets are quite soft aluminium anyway).
and here's the spacers added and secured.
By the way I chat with Hans from HP Performance from time to time, so if this works, I'll pass it on to him so he can consider doing that mod standard with his kits.
My driveway runs by my 3 year old's bedroom so no testing til tomorrow sorry! I'll be trying to keep my expectations in check until then.
Edit: Looking at your damper piston and rod, looks like you may have had less play in yours. A quick google image search shows dampers with much less play than mine. Such as below
Edit 2: Also interesting is this article...
http://mgaguru.com/mgtech/carbs/cb105.htm