2006 Chevrolet Trailblazer P0171. Can't find the cause

With my 2006 Trailblazer I6 I had had the P0171 code on and off for awhile, but it eventually became a permanent thing. Both the method of spraying carb cleaner around and the use of a smoke machine indicated that the intake manifold was leaking. I decided to just tighten the bolts and see if that would solve the problem instead of replacing the manifold gasket. There are ten bolts and the ones closest to the front of the engine were not loose, but as I moved further back the bolts became progressively looser. Towards the middle of the manifold the bolts were definitely loose requiring perhaps a quarter turn to tighten them, the ones toward the rear took perhaps a full turn, and the very last one probably two full turns.

I used a variety of 1/4" drive tools to get the job done, including a variety of extensions including wobbler extensions, universal joint, and regular and 10mm deep socket.

I did unbolt the ECU to improve access, as well as removing the large vacuum hose going to the brake booster. The front ones would be much easier if the alternator was removed, but I left it on. I also disconnected the battery because toward the rear of the engine the hot terminal of the starter is fairly close to where you will be working with your sockets.

Each bolt posed its own particular challenges. I suggest you do not do this when you are pressed for time.

The problem is solved!