P219B code, trying to trouble shoot.

[tig488]

2014 5.3L AT, 125000 miles.  started getting the P219B CEL, bank 2 air fuel imbalance.  no real symptoms except for some hesitation when accelerating uphill or passing but dont know if thats the crappy tranny.   things ive done so far.  swapped O2 sensors from R to L.  new spark plugs about 10000 miles ago. regapped and swapped banks.  same with coil packs and plug wires, swapped banks.  new PCV and solenoid.  started getting the lifter tick about a year ago so removed valve covers to check rocker arms and lifters but they are all good.  no issues there.  bought injectors but havent replaced them yet.   ordered a vacuum tester to check for possible vacuum leaks and compression guage to check cylinder pressures. 

 

can anybody else think of anything i havent thought of.  im gonna be pissed if put in new injectors and still get the code. really appreciate any other suggestions.