I'm not sure if this is the right place for this, but I've been doing a bunch of searches for things and Google/Yahoo bring up many past TC posts with keywords that don't bring up anything in the TC search. Is the TC search limited in how far it goes back or is there some other difference?

Which TC search?
There's one on the toolbar that has 'user cp' at the left side ,and there's the 'Google custom search' below that in the center of the page.
I get good results with the 'Google custom search'.