Neo, I ordered the service manual for Midliners, and should receive it Tuesday. I will do my best to keep up with you on the 3 post's you have, and send pic's and info accordingly.. I still think its easy to find the air leak when you hook shop air to the truck. I would un hook the air supply from the compressor at the tank. Install an air line coupler into an open port that may have a plug in it, or install a 'T' fitting behind an air line that is coming out of the tank, then install a coupler into the 'T' and reinstall the air line. this way you have a test port, or a port to air up the truck, for other reasons. once this is done, the air compressor line that you removed from the tank is set aside and a plug is screwed into the tank. now you have isolated the compressor and closed the the system from the tank outward. put shop air to it and then crawl around and find the leak... I have a couple of air nipples screwed together for this type of testing. jojo