Mark,
After a similar experiance with my first YS .63 (in a .40 sized GP CAP 232) I bought a second one for my Sig Fazor. I am just as pleased, but had a different experience to start. After falling in love with my YS 1.20, my YS .91 AC, YS .53 and YS .63, this latest .63 just would NOT run right. I was shocked and convinced that I must be doing something wrong. Finally, I gave up and admitted to myself that every engine maker gets a bad one out now and then, and after a call to the importer, sent it in for warranty repair. Well, this weekend I took the returned engine out. The slip in the box indicated they fixed a problem with the plunger in the regulator AND, for no charge, they update the engine with their NEW piston design.

Now, it runs just like it is supposed to, and like your set-up, with an APC 14 x 4 wide, OS type F plug and 27.5% Nitro fuel (I custome blend my Nitro percentage), it hauls my Fazer around like mad.

I am once again pleased. They had a problem with this one from the plant, but got it fixed right up and it now runs like a champ...

Lee