Dreaded P0174

After performing the TSB, and I had it almost surgical clean... The P0174 is back, and I can only drive it about 10 miles or so before it comes back. This is not intermittent.
The short term fuel trim numbers (I can look at them real time) are WAY higher on bank 2. The O2 sensor voltages are somewhat lower on the bank 2 sensors as well.
Is there ANY chance that a bad upstream O2 sensor can cause this without throwing a code on it's own? Man, I'm tired of this code in my face. Emissions inspection is due in November as well.
Any help would be appreciated.

It could be a number of things.... but it could be the MAF as well needs to be cleaned :
http://www.sparkys-answers.com/2009/02/2003-ford-windstar-p0171-and-p0174.html

but as for the o2 sensors you would need to find out what one isn't working properly most likely the one closest to the exhaust manifold.

I had the p0171 and p0174 on my 2001 and i did the port seals,valve cover,pcv,plenum gasket,isolator bolts,air cleaner,soaked the MAF in brake cleaner while i was taking the van apart and cleaned the egr ports while i had it all apart it was a little time consuming but i did this about 2 months ago and the light hasn't come back on van still reads 0 codes but i have 1 sensor that won't reset i guess i need to take it out on the highway for a run...I forgot how much fun it was to work on cars especially right after you drive it off the lot:banghead:

You might try switching the sensors from bank-to-bank to see if the code "relocates".

.....and don't wait 'til the last minute to get the car emissions inspected. That's what I tell my kids .... they don't listen either! GA will let you get it inspected 6 mos. early, I believe.

Actually it's 12 months in GA and you can have 2 of the indicators incomplete and still pass. That's how I got my camry through with the bad cat'. Reset the codes and wait until only 1 or 2 are incomplete then run and test real quick. (muahah)

Bank 2 is the front one where the PCV is. I would take a very close look to it and it's related tubing. Is it's an old valve, you might want to try replacing it, it' a wear item and it's cheap maintenance.

Did you replace the valve cover too? Maybe it's not tight enough and it's causing that bank to go lean.

Oscar.