I remember before I got into the XML files and turned something from I think YES to NO, or something similar, and I was able to disable techs past a certain point in that way, making it so you couldn't advance past the medieval era, or whichever I wished.

The problem is, I can't remember how I got in there. I would also like to make the tech cost a lot more, so it takes even longer to research a tech.

Can anyone help?

There are one or two modders here who may be able to help. However, the general Creation and Customization forum is probably a better place to post, as there are far more modders who live there.

I figured it out.

In case anyone is wondering, in the XML file called Technologies, change the number of the tech cost to whatever you want for that tech, and to disable a tech, change the '0' to a '1' in the <bDisable> tag.