Check Engine Light - P1124 and P1126

[GoodJohnny]

OK, I have undergone quite an adventure with my Boxster and wanted to share my experience and results of a viable solution to this problem of Lean Run at Idle. I am trying to be detailed here, so please excuse the length of this post.

First off, I have access to SnapOn Scanner and Emissions Smoke Tester, as well as a facility with multiple vehicle lifts… these did help a lot. Also have Durametric product. All these are definite advantages, the two former more than the latter as my previous laptop was a dinosaur. I WOULD NOT HAVE BEEN ABLE TO DIAGNOSE THIS WITHOUT SMOKE MACHINE.

Symptoms and Codes:
P1124 and P1126 - when the engine detects a lean run condition at idle and enriches the fuel mixture to maximum to compensate.
I also had a verified bad Mass Air Flow Sensor. But that's not really germane to this discussion.
My symptoms were, initially, backfiring through the intake.

Work Done:
It was time to replace the upstream O2 sensors anyway so I did that. The new ones read much faster on the scanner.
I hooked up the smoke machine and first leak was vacuum line from rubber intake boot (bank 2) to fuel pressure regulator. Fixed that.
Then the opposite side rubber intake boot connection and hoses on bank 1 side were leaking. Fixed that.
Changed fuel filter, clogged. Checked fuel pressure, perfect. Checked pressure regulator operation, perfect.
Wasn’t until I had all these leaks fixed that I found Oil Separator leaking. Replaced that and J-tube.
Smoked the care again… smoke poured from spark plug tubes, cylinders 4-6. At this point, I was becoming frustrated. Cylinders 5-6, removed coils and cleaned outer surface with brake clean. Applied neat a uniform coat of black RTV silicone. After setting up, no more smoke there.
Smoked car the last time. Cylinder 4, pouring smoke. The same RTV trick didn’t work. I removed coil and where the sealing rings are on the coil boot, inserted high temp o-rings. This sealed the air leak.

Finally:
I know this is some serious jerry-rigging. But until I reach a magic mileage number or the engine goes poof, not rebuilding this car. It runs far too well and my enrichment readings are acceptable. I have 155,000 miles on this Boxster, 27,000 in the last 11 months. I drive it like it was meant to be driven and have, until now, only performed routine maintenance.