I am on page one, listing 2 in Yahoo out of about 41 million results and page one, listing 3 on MSN of about 8 million.

I would like to critique the website some more for Google, but I don't want to somehow lose my ranking for the other two search engines. Is adding more or doing more seo a bad thing?

I have PR4/5 throughout my site as well.

Google takes more time and is more picky than the other engines... you have to try stuff and get links... not too many at once but get links...