I have a power commander 3 someone gave me they dont know what its for or the bike it came off of. How can i find out if i can use it on my bike which is a 2001 600 f4i. Im really hoping its for mine but im not sure any help would be thankful

 

Unfortunately not at a glance as the units are basically the same for all bikes, it is the harness that dictates fitment.
You could try to see if the loom pictures in a manual seem to be the same or...
Try it, the main connector is on the L/H side of the tank and is quite readily accessible, you should know in an hour or less if it will fit.
If it fits you should be good to go!!