Walt, I suspect that there are several places that could bore your ITBs larger. I can think of a few off the top of my head.
Aaron Burnham at RennWorks
and a great shop for weber refurbishment
Performance Oriented
I also suspect Bieker Engineering (SP?) and Eurometrix could also do this work.
Congrats on the Personal Best! This is always a good feeling and that is quite a jump.