Hoping for some help from the most active Argus forum/thread, which prompted me to buy the A5 recently. Came with a Hong Nor 2080 pipe.

So I had my LHS run it in for me with the extra shim. He only put about 3-5 tanks through it and I put the rest of a gallon of 25% Byrons. About 3/4 through the gallon, it still wasn't developing much power so I took the extra shim out. Got a noticeable jump in power, but still not what I would call lively.

Just checked and the shim in place is .20mm. I can't seem to find the other shim, which I presume would have been the .10mm. Whilst checking the shim, I noticed some light pitting on the piston and the filament is a bit white. Is this because I'm running lean?

Temps are around 260 deg F or 125-130 deg C.
Glow plug is T3 (alpha?) that came with the engine, but I have 97T O'Donnells I can use instead.
I'm in UK, so ambient temp isn't very high.
I have 30% Ammo fuel I would like to use, but can stick to 25% Byrons.

My main question, is what size shim are people using? I've read most of this thread and searched for references to shims. Someone reported they were running 30% on .40mm shim during break in and .30mm after. Most other references to shim simply state whether they were running with or without the extra shim etc, but don't mention what size shim is left in place. Should it be .20mm on 25%?

I've also found some information about pitting being due to running lean or incorrect shimming, but again, the information I've found doesn't mention whether pitting is caused being over or under shimmed.

Would really appreciate any help, John

P.S. I'm not allowed to post links yet, but will add pics if required once I've made a few more posts.