Ws6Dnero

iTrader: (23)

is there a specific way to wire the 9" fan up or do I just connect the fan to the factory harness and be done?

LS325ci

iTrader: (3)

run a relay straight to battery.
use an inline fuse.
energize your relay using factory harness.

I dont know what the draw of your fan is but my derale fans used a lot.

ramairetransam

iTrader: (18)

i ran my second fan to run when the first does .

Ws6Dnero

iTrader: (23)

Also as for amp draw, i have a higher amperage alternator & 0-gauge wiring in the car so my voltage is higher & more stable than normal.

But anyway so run a relay in between factory harness & fan or is it needed with the electrical upgrades I have already?

LS325ci

iTrader: (3)

I always recommend aftermarket fans to be run on a relay just because you dont really know the condition of factory wires. Last thing you want is melting some stock wires/shielding.

your upgrades is a separate thing from the relay. UNLESS you upgraded your stock fan lines.