bank 1 lean

CEL came on. bank 1 lean. No engine work done recently. Fuel pump is audible. Engine starts, idles, and accelerates fine. I cleaned  MAF w/ electric parts cleaner. I used an Actron code reader to erase. Code came up again but no CEL. I will assume it will soon. Gonna test the fuel pressure w/ a gauge later today. 

My thoughts are a bad fuel pressure regulator, or bank 1 O2 is fouled up, or the O2 took a poo.

I will clean both down pipe O2 sensors, label them and swap them bank1 to bank2......   See if anything comes up different. If not, I will purchase a fuel pressure reg pending fuel pressure gauge results.

Anyone think I am missing something for this P0171 code?
 
 
 
 
 
 
attachment is a secret.

Sounds like you've got the bases covered.  I don't think it is an FPR issue though...  Could be an exhaust leak...

Has the idle speed changed any? I've seen a leaking intake gasket cause this code, but it was accompanied by a slightly high idle due to the vacuum leak.

Idle speed is normal. 600RPM or so Couple quick pulls of the throttle cable it idles fine. I used my pops vaccuum gauge and the needle stayed steady. Got good vaccuum. I purchased a fuel pressure test gauge $35.00+ at A-zone, and it was in a normal range, key on engine off pressure was at 50 psi? I think?, idled the Blazer, and a little brake stand. (RPM's up to 2k.) Lowest was 45 psi the old man said.
 
I erased the P0171 code. And restarted. No codes stored yet just from idling. After I get my Sunday paper at the store I will look for the stored code.
 
Probably need a good run to get the PCM to get a reading from everything.
 
 
If it come up again, I will swap the O2's. Kinda chilly out and its getting late.