Factory front lip second install
 

Apologies if this has already been asked, I couldn't find any results.

I tried installing an ebay front lip that used self tapping screws and didn't like the fitment so I took it off. Now I got a couple of holes under the car. I decided to skip the hassle of fitment issues and just order an STI lip. Will my previous drilled holes be a problem for my next installation?

Should be fine.

Agree, the lip is not structural so even if you end up with a couple of figure 8 holes there will not be an issue.