Do they tune nitro rc cars here?

Yes they do.

They have a full service department. They used to have a teach and tune service unsure if it's still available.

When I was there, not too long ago, looking for lights for my Traxxis TRX4 Land Rover Defender, my new "R/C Sensei" Paul, started up a nitro car right in front of me. It needed tweaking, but he got it going. The point is, when you go there for whatever reason, hang out, and you will learn so much as Paul, Thomas, and Kevin are doing their thing.