I have a 2002 Chevy S10 Blazer 4 door 4WD 4.3 liter V-6 with 210,000 miles.
The check engine light has been on since I purchased it back in 2020
I have taken it to several mechanics over the years and no one can figure it out.
The code is for left cylinder bank running rich.
One mechanic replaced the Engine control module, crank sensor, spark plugs/wires, cap and rotor.
Light still on for same code.
Then a second mechanic replaced the fuel filter, mass flow sensor and temp sensor that wasn't it.
I had a 3rd mechanic replace the PVC valve.
That wasn't it either check engine light still on for same code.
Bunch of money wasted.

Any other ideas what could be the cause of the code for left cylinder bank running rich?
I know it'* old but it is doggy and lacks power.

You need to find a decent tech who tests things rather than your parts exchanging mechanics.
Do you have anything that shows testing they've done. Fuel pressure?

No I don't have anything that shows the testing they have done.
I have been trying to do research on what the problem could be.
My leads have me believing it'* something to do with the intake manifold and vacuum pressure.

I would bet the intake gasket needs replacing. Common problem on these. Do this. Use an external fuel source, ie propane torch, can of carb cleaner etc. and with the car idling go around with the torch (UNLIT) around the intake. Does the idle change at all? Yes. You found your problem. No. Doesn't mean it'* not bad.

Thanks for the advice I'll try that out tomorrow.

I agree, your car has had parts cannons unloaded on it.

I'd go after the intake manifold gaskets first, then look into possibly having a bad injector.

Ok today I took a brand new can of carburetor cleaner with the little plastic hose attachment and spray down the intake manifold while the engine was idling.
I didn't notice a difference in the idle.
I watched a YouTube video of someone with the same code and they replaced a fuel pressure regulator that is located under the intake plenum.
I wonder if it'* the fuel pressure regulator?

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Get a pressure gauge with the hose. Less than 25 bucks. Guesses stink.

Yup . . . .

Update:
Well it'* been over 4 weeks since I replaced the Thermostat and cleared the codes with my little code reader.
The check engine light hasn't came back on and it is running better.
I went from 14 mpg to 18 mpg.
I bought a fuel pressure tester kit but I haven't tried it out yet because I believe I solved the problem.
Thanks for the advice everyone.