I installed some new plumbing lines in the basement (stubbed). Now when I turn on the hot water upstairs it doesn't get very hot. Anybody have any ideas? Air in the lines?

Have you perhaps tied a cold water line into the hot? By stubbed, do you mean you have run lines for a future installation and have them capped off? Even if you have tied in a long loop that is letting the water cool before it makes it upstairs it should eventually heat up. How are the other hot water outlets working now? I'll bet you are mixing hot and cold somewhere.

Adding pipes will not change the temps of the hot water at all. What will change the temps is.
Hot water heater is turned down. Or you cross connected the hot water pipe with the cold water pipe. The result is the mixing of the two pipes causing cooler water temps at the tap. That is all that would cause the temps to drop.