I'm still chasing the strange gargling exhaust noise at 1100 RPM. I replaced the O2 sensors, the EGR valve, the EGR vacuum regulator, vacuum lines, and the coolant temperature sensor. The catalytic converter test completes green, the O2 sensor and O2 sensor heater test cycle completes green but I'm still getting an EGR "low exhaust flow" warning error code. I think the gargling noise is from an incorrect mixture due to the EGR malfunction. Something occurred to me today, are the two vacuum lines to the side of the EGR vacuum regulator interchangeable? They appear to draw vacuum/boost from the same place so I didn't pay careful attention to which line went to which fitting on the regulator. See the picture below for how I have it now. 1. are they interchangeable? 2. do I have them set up incorrectly?
