definatly something electrical...

lemme ask this... have you reset the computer after the tune-up? To do this... look for the ECU fuse... usually the radio memory fuse in Hondas. Pull it out and leave it out for like 15 seconds... re-install the fuse and drive the car for a while.
Sometimes, the computer will "store" the code, and keep the CEL on till the computer is reset.