I would say go with an intake, not too expensive (around 200), yet a nice improvement on the car and something anyone would love to have. Plus install is a breeze.
That is really tthoughful of you to get him something for his car, my girlfriend also tried to get me something for my car for christmas last year. She registered and asked some questions but didnt want to get something i didnt want, so decided to forget it. Even though she didnt get me anything, i was really happy that she went through the trouble to try.