I am new to the LS motors scene and having problems with rough idle and surging when the electric fans come on.
My MAF sensor is in an elbow coming off the TB and the sensor is only a couple of inches away from the dual fans.
Someone suggested that my rough idle is due to fan wash.

How do I fix this?

 

Your MAF is not being bothered by fan airflow unless
you don't have the ducting in front of it.

If you can't see a body-block-PCM ground offset
develop with the fans on then you can pretty much
rule out electrical effects.

I expect the issue is more the incremental shaft
load (through alternator & belt) to run the fans
and perhaps the A/C compressor if that's why
the fans are on, against a messed up torque-for-
air-mass model and a messed up air mass model
at the low end, which is a common consequence
of airflow mods.