look at the valley on the motor. if the cover is smooth its not an afm. if it has a network of passages it afm.
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scroll to the pic

 

LS Engine Tech – Active Fuel Management (AFM) (summitracing.com)

can also look for the engine rpo code.

 

I'm not going to take things apart just to look at "the valley"

I get this from https://www.vindecoderz.com plugging in my VIN number
"(L94) ENGINE FLEXIBLE FUEL,(GAS/ALC),8 CYL,6.2L,SFI,ALUM CYL DEACTIVATI " so that seems to confirm that my engine has it, along with the DIC screen reading.

 

If you put the dash info screen into the real time mpg mode and it shows V8 it's an AFM motor.

 

you don't have to take anything off.
if you have l94 build code, you have afm.

 

I changed the oil and filter today, and re-set the oil life indicator. Was messy removing the oil filter.