I keep getting a p0171 and p0175 codes from the scanner (auto x-ray)(meaning i'm lean in bank 1 and too rich in bank 2). fuel injector cleaner didn't help really help. so should i replace the upstream O2 senors or the fuel injectors... any other suggestions would be appreciated. thanks.

P0172 LEXUS - System Too Rich Bank 1
Possible causes
Faulty front heated oxygen sensor
Ignition misfiring
Faulty fuel injectors
Exhaust gas leaks
Incorrect fuel pressure
Faulty Mass Air Flow (MAF) sensor
https://www.autocodes.com/p0172_lexus.html

P0174 System too lean, bank 2; Possible causes, Intake/exhaust leak, fuel pressure/pump, injector(s), AIR system, hose connection(s)
P0175 System too rich, bank 2; Possible causes, Intake blocked, EVAP canister purge valve, fuel pressure, EGR system, injector(s), HO2S
***Try shaking out the air filter. : )

P0171 ; Fuel Trim System Lean (Bank 1)
P0174; Fuel Trim too Lean (Bank 2)
fuel trim is system to modify injector pulse if system go lean it will go rich when the system is too much lean and is max.rich it code
look for 02 sensor bank 1 and 2 data
hope it helps

code p0171 refers to system too lean bank 1===causes ---intake /exhaust manifold leak---ARI system--MAF/VAF sensor--fuel pressure /pump---injector/s---ECM
code po172 refers to system too rich bank 1===causes --intake blocked---EVAP canister purge valve---fuel pressure---EGR system---injector/s---HO2S

PO 171 Bank 1 too lean
PO 174 Bank 2 too lean
Why ?
The front O2 Sensors need to be replaced at
100,000 miles or sooner, if they have actually failed
They are reading too lean because the system is too
rich & the computer is driving the fuel trim or injector
pulse lean, thus the codes or failed sensors, yes both
Have to check fuel trim with a scan tool
Have to check fuel pressure
Have to check there are no leaking injectors
Have to check for Vacuum Leaks from the intake
all the way to the exhaust converter
Your working a rich condition keeping in mind the system
is driven lean
You look at fuel trim short & long,sort of a past history
of events
May want to look at converter temps also
The converters won't last long if you have or has
a rich condition from fuel or cylinder misfires
Now the spark plugs can't be over 3 years old
& no mifires,get that out of the way before working
the O2 issues

P0171 System too lean bank 1
P0174 System too lean bank 2

Last time you changed your fuel filter?
Look for any vacuum leaks.

You have big problems here, I suggest you go to the provided links and read about these fault codes and then hire a good technician.
Ford P0171 P0174 Lean Codes

P0172 OBD II Trouble Code System Too Rich Bank 1 YourMechanic Advice

https://www.obd-codes.com/p0175


P0304 OBD II Trouble Code Cylinder 4 Misfire Detected YourMechanic Advice

P0171 System Too Lean Bank 1
P0172 System Too Rich Bank 1
P0173 Fuel Trim Bank 2
P0174 System Too Lean Bank 2

OK, that's a partial list of codes, the fuel delivery is controlled by the oxygen sensors, so it's possible that something in that area could be causing your problem.

However, it could also be clogged fuel injectors that can't deliver enough fuel to the cylinders compared to the air that is pulled into the engine.

Try some fuel injector cleaner for that poured into the gas tank.

How does it run?
Does it miss at all?

those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .

Check for vacuum leaks around the intake. This is the most common cause for these codes.