I figured it out. RegEx are slow. Period.

I got rid of my RegEx and just used IndexOf(). Even if I need to do multiple searches on the same line to qualify / disqualify, it is MUCH faster than a single RegEx. Even simple RegEx like "MyNameIsBob" is much slower done as a RegEx vs IndexOf().

Now that I have changed over and gotten rid of them, it is parsing this file very quickly.

The moral is:

Do not use a RegEx unless you absolutely have to. They are very, very slow compared to a simple string search, or even several string searches.