Ok, so this is my sisters car and she has been getting intermittent CEL. The code wasn't happening frequently and a shop told her to drive and and see if it comes back. Well it did and this time the P0173 was pending. So based on what I have read here this is most likely a vacuum leak. So tonight when she came over I used the Torque app to see what her idle vac is, well it was 0.7...so needless to say there is a leak and it is pretty big. Since the engine was hot and it was getting dark I couldn't really poke around. But I was hoping someone could comment on which lines are the most likely to fail. Also, can someone confirm what is mounted on the firewall that has a barb fitting on either side of it? Not sure why there are two fittings without any lines going to them...ideas?