P0174 FT too lean bank 2

04 Ford Ranger XLT 4.0L.  Problem apparently began after vehicle was at body shop for over 7 weeks.  Damage area was to RF headlamp/fender/hood.  Vehicle was taken to a shop where they replaced the MAFS, Intake, coil pack, plug wires/plugs, fuel filter and fuel pump.  They said they disconnected cats with no change, then they gave up.  Initially P0301-303 and P0174 were stored.  Cleared dtc's and only P0174 returns.  STFT bank 1 close to Stoich, LTFT bank 1 -9% to -12%.  STFT bank 2(at idle) 25% within 15-30 seconds from start up, LTFT bank 2 25%. At 2500 rpm STFT B2 will drop to 3%-5%. I do not hear a vac leak and have sprayed this engine with enough carb cleaner to choke a bear.  O2s and FT do not react when spraying to find leak.  I removed vac line and sprayed carb cleaner directly into intake and do see that O2s and FT do respond.  All injectors ohm at 16.4-17.4(engine at operating temp).  I can see with a scope the bank 2 injector pulse is slightly longer than bank 1 and they do respond to throttle snap.  O2s, via scope, are switching however rears are B1 .70 and B2 starts around .60 then will drop to around .28.  I've verified ECM power/grounds are good/clean. At idle there is felt a slight stumble from the engine, using Fords IDS and power balance test, shows cylinders 1-3 as being weak. Electrically I don't see anything obvious, mechanically the engine sounds/drives fine(no ticking/knocking/etc). Both front/rear O2s have been replaced along with the ECM. The way B2 FT is reacting it acts like a large vac. leak.  But does not explain why B1 is opposite. I wouldn't think timing would be off, no dtc's and vehicle starts/runs fine.  Thoughts? 

Please correct me if I have read this wrong. My reading of this is your Bank 1 long term and short term trims are all trending negative ie. rich and Bank 2 long term and short term fuel trims are positive ie lean. Have I understood what you wrote correctly? Thanks.

Correct, soon as closed loop bank 1 goes -12 and bank 2 goes +25-+35. I've swapped injectors from bank to bank with no change. Again I've sprayed engine/exhaust/etc with soapy water/brake clean no seeing any leaks/change to O2 response.

Any lose of power issues? If you have sprayed around the engine and no vacuum leak issues- you may be looking at restricted exhaust on one bank.

No loss of power. Vehicle runs good. Cruises along fine at all speeds, WOT do not notice any stumble/hesitation or loss of power. Prev. shop said they disconnected cats with no change. I've noticed today at about 2500rpm both banks STFT will come down close to stoich. All indications are a vac leak that I apparently can't find. But does not explain why bank 1 acts rich at the same time bank 2 acts lean.

I would do a wide open throttle run and graph the 2 upstream sensors and the inlet air temp pids only. If this test is good, I would then test for back pressure in the exhaust. Paul has some great videos of the test on you tube.

Will try that and see what happens.

On a side note see the post on this forum : O2 sensor full throttle test/ on road test created by Raysmb.

Back pressure sits at or near zero on both banks from idle to 3000 rpm. Snap throttle and barely hits .5 psi. Going to perform road test and monitor O2s.

Ran WOT and monitored IAT and front O2s.  Hopefully my attachment shows up, not very computer savvy, lol. 

When you get a chance take for a drive and graph both the long term and short term fuel trims for both banks. I would throw in calculated load % paid also. Your O2 sensors did what they should at wot. I see the upstream sensors were replaced, I would just confirm not a chance O2 harnesses accidentally got switched and plugged into wrong banks. Just nice cruise, do not need pedal to metal. Just curious, is Bank 2 Sensor 1 switching normally?

Will have to road test another day. Will update after next road test. With scope, O2s were switching nicely. With IDS and graphing PIDS, they are erratic, same with Autel. I'll try and upload other pics shortly.  The O2s are connected properly. Bk1s1 connects at the back of block near bk1 head.  Bk2s1 connects under vehicle near shift linkage of trans.  Both rears are similar, BK1s2 connects near the starter and Bk2s2 connects near the top rear of trans.  The harnesses are not long enough to switch connection points.  I double checked that early on. 

In your initial post you said bank 2 sensor 2 started out holding at .6volts and then drops to.28 volts. That is why I am curious what Bank 2 sensor 1 voltage is doing. Thanks.

Correct. BK2S1 seems to still be switch regularly even when S2 drops to .28mv. When I road test again, I will try and capture a video, upload to the Tube and share the link.

Road tested from cold start to operating temp. recording LTFT/STFT and engine load.  Trying to get video uploaded to youtube to share.  Also recorded front/rear o2s along with MAFs.  Not sure about MAFs reading from Autel, it differs from IDS.  Vehicle did have OEM mafs, i replaced with a used one from an 09 ranger, same part number, no change to fuel trims. This is the link for the O2s recording,  
Once I have the other file uploaded I will send link as well. 

Here is the link to LTFT/STFT and engine load. This  was from cold start to operating temp. The O2s video is at operating temp.

will take good look at graph later, but initial misfire code, did it set before lean code issue? Did they happen to tell you why they replaced intake manifold?

Previous repair shop said intake had a crack in it, as the reason for replacement. I will have to check original scan, but i believe misfire dtc’s set at the same time originally. The misfire dtc’s have not returned since I have had the vehicle. Not sure if I will have freeze frame data. Will update once I check.

Your O2s and Mafs video - I noticed the mass air flow sensor read 0 until into 1 minute 15 seconds of the recording. If there are no vacuum leaks anywhere, and you can not find any -this displays all the symptoms of a bank blockage, but your back pressure test throws that thought out the window lol  I think time to put a smoke machine on this truck. Thoughts anyone?