2004 Mazda 6S Lean Condition Under load

I have a 2004 Mazda 6 S. that is giving us a P171 and P174 when under load. It started originally with it at idle and under load. We found several vacuum leaks and fixed all of them. Cleared all codes and drove the car for several days. We also reviewed the LT and ST fuel trims while driving. And at idle long and short term are under 5% total. But under load LT moves to 20% bank1 and 15% bank 2 with short term being around 10% on both banks. We have done a fuel  pump test to include volume under load, dead head test, and pressure testing which does not show any issues. 

1. Fuel Pressure 60 PSI
   1. Very slowly drops i.e. 2 hours to show 10 PSI drop in pressure when KOEO
2. Fuel Volume .9 Gallons per second on a flow test. 
3. Dead Head test only jumped 10 PSI and still reviewing that a bit more. 

Upstream O2 Sensors fluctuate and seem to report like they are supposed to both are always moving between .2 volts and .9 volts in a solid updown wave form. 
Downstream sensors seem off to me as Bank 1 usually sits about .8Volts but does fluctuate to .6 volts. If this was controlling fuel trim, I would expect it to show rich condition and fuel trims to be negative. But could be wrong as I know some cars the downstream is what is used to adjust fuel trims. 

Right now I think my focus should be on Injectors and Down Stream O2 sensors. My gut tells me to replace the O2 sensor but I do not want to be a parts changer. Any suggestions would be highly appreciated. 
 

Out on the highway, what do your upstream O2 sensors do at Wide-Open-Throttle acceleration? Do they go full RICH? Or, do they fall LEAN? Does fuel pressure remain strong under acceleration?
If the O2 sensors fall LEAN, but Fuel Pressure remains strong, you may have a fuel volatility problem.

I will test this tonight. I do have the ability to test flow for he fuel pump and it tests good. but will validate under load just in case. And graph the o2 sensors later this evening. Thanks for the input.