Yes I hear a hissing sound but cannot seem to find it. I am having a new water pump, timing belt, iac, and egr valve put on by my friend next week and I'll ask him to search for it then. I've tried spraying carb cleaner all over but no dice in terms of locating it.
Aside from that, it could be that the fuel pump is going bad or a bad injector, so I just put in Lucas Fuel Injector treatment to see if that helps. A re-cleaning of the maf (first cleaned it just last week) helped smooth out the hesitation issue I had earlier, but the idle is the same. Reading through a ton of posts, it seems like maybe I should be patient until next week and hope that the egr/iac replace effects things for the better. Seems like people have had code 172 fixed in many different ways.
