Ford F-150 (2004-2008) :: Lean Condition Bank 1 And 2 / Random Misfire

2006 f-150 with a 4.6L. Its got 175k on the clock and ran like a sewing machine despite little maintenance other than oil changes. Recently it started running like crap; no power and missing so he borrowed a scanner and it was giving multiple codes. Here's what we have done so far, not necessarily in this order :

1.Checked for vac leaks with carb cleaner (this can be tough as engine runs crappy and hard to detect minor changes in rpms while your under the hood) no leaks detected yet

2. Changed the plugs, all looked good except for one which was heavily fouled and the electrode ate away mostly, I wasnt there and he doesnt remember which one but have a suspicion, more on that in a min

3. Changed most of the COPs and checked them all with a spark tester, all are firing.

4.Cleaned the MAF sensor with MAF cleaner

5. Checked back pressure on the exhaust by removing an upstream o2 sensor and holding a plastic fitting hooked to a pressure gage long enough to get a reading, about 1 lb idling to maybe 2 max when engine is reved, gage is not the best and fluctuates a 1/2 lb or so. Exhaust does not smell of rotten eggs.

6. Changed the fuel filter, it was terrible

7. Ran a bottle of Seafoam in the tank

8. Took the throttle body and egr valve off and checked for carbon stoppage, the holes in the egr were not blocked

9. checked the PVC valve and line and both elbows

7. checked the injector connectors with a noid light for signal, they all flash, checked the injectors them selves with a multimeter set for ohms, all about from 13.5-14.5. This should mean they arent fried but could they still be stopped up? They all sound like they are pumping when you listen with a mechanics stethoscope

9. Changed all 4 o2 sensors as this had never been done anyway

10. Compression check on cylinders, all within 10% of each other at about 180 lbs. When we pulled the plugs they all looked good except for # 7 which was heavily fouled ( I suspect the same on the original plugs) and again with a bad electrode, the part coming out of the porcelin. Intrestingly, this was an autolite plug, the rest were motorcraft, I hoped this was somehow just a bad plug but no change with a new MC plug

11. Changed the injector on #7

The scanner reads lean condition on banks 1 and 2 and random misfires on #4 and # 7 still. Per a troubleshooting tip online, we sprayed some carb cleaner in a small vac line coming off the manifold to induce a rich condition and the scanner showed the o2 sensors go to .900 which is what they are supposed to do per the guide. This means they are functioning correctly and a bonafide lean condition exists. I am leaning towards a vacuum leak around the plastic manifold under the aluminum one, maybe the gaskets but would like to rule out the egr valve, could it be the culprit?

I have even considered the possibility that the PCM is bad, though not likely. I have read to detect a vac leak you can hook the scanner up and spray the carb cleaner around on the manifold and lines with the scanner hooked up watching the scanner PID for the o2 sensors and when they detect the cleaner, they will hit that .800-1.0 meaning the engine sucked the cleaner in and you have found your leak. The exhaust smells rich. If it is a vac leak, you would think it should be a massive leak and not hard to detect, as crappy as the truck runs. I have searched the forums for days and exhausted about all I know to do.

Most important note: early on I suspected low fuel pressure as a possibility; with no schrader valve on the fuel rail and no easy spot to T into the system, we were scratching our heads how were gonna measure psi but the scanner reads absolute fuel rail pressure, gives about 40-43 psi. I hope the scanner is telling us what we need to know there, would prefer a mechanical gauge on the rail!