Wow a little long but I will try to help....

First off on break in wher eyou running 1 full tank as a cycle or 2-3 minutes for a cycle. Not sure what break in method you are using but the heat cycle is by 2-3 minutes runs not tanks....

I run a 528 in my lsp, and it was one of the easiest to break in, but one thing about it, it is very sensitive on the low speed needle, I barely ever touch my HSN. This is different than most of my other engines. Most people I know that have tunning issues with this engine, is they are to lean on the lsn and to fat on the hsn. I run the same plug you run all winter long, with no probs.