Confused by Fuel Trims: Why two banks for 4cyl?

I'm trying to troubleshoot a cold start issue. So I logged some data with my bluetooth OBD scanner and I'm curious as to why my 4cyl has 2 banks of fuel trims? At idle one bank appears lean and the other appears rich but as I start driving and hold a higher RPM they both seem to go lean with one bank being much more lean than the other...any help interpreting these would be much appreciated.

 

I'm not sure why it's showing two banks because it only has one but bank1 fuel trims look pretty normal.
I read through your other thread and based on symptoms I'm thinking you have a fuel pressure bleedoff problem.
You would need a fuel pressure gauge tapped in when the problem occurs to confirm (fuel pressure should not drop below 21 psi for at least 5 min after engine is turned off) but that's the classic symptoms.
When the fuel pressure is allowed to bleed off there will be no fuel in the rail when you go to start the engine and it takes time for the fuel pump to build pressure, when the engine is hot the problem will be worse because without pressure the fuel will boil in the rail and force everything back to the tank leaving nothing but vapor in the lines so the pump has to prime everything back up.
If you determine that is your problem you will have to pinch off fuel lines to determine if it's the regulator, injector leaking, or faulty check valve or seal in the fuel pump.