Have him unhook the battery for about 10-15 minutes to clear the computer. Hook it back up and let the computer relearn the intake flow, it seams to be hit or miss on these cars liking the intakes or not. I did not have a problem with mine but some do. I believe the code is showing up as a lean condition (too much air) go figure. Give it a try and let us know. also double and even triple check that everything was installed correctly. Good luck.
happened to me when i inatalled my intake... same code.. i had a cheap maf adapter which was the problem.. if he can ask him to use couplings to attach the original maf adapter to the air intake filter.. not sure if it can be done on the newer generations, but i did that and my cars cel of p0171 never lit back on, sometimes the sensor not sitting right causes the idea of it running lean