TB42 Air Intake

That big black cylinder thingy, is the air cleaner, which is of the Cyclonic type. The 'stationary fan' is there to spin the air as it enters the air cleaner and the motion throws all those DUST/DIRT particles out that KILL ENGINES!!! Hence the need for the air intake and cleaner system!
Can you imagine tha amount of unfiltered air you just sucked into your engine and the masses of particulate that wil now be in the oil scouring your bores and wearing the bearings!

Keep it where is is if you like your engine to perform as it does now, or remove it for a small increase followed by a huge decrease in a short time!

Any mods to the intake system should be done by a pro and all are usually forward of the aircleaner, not after it!!!

Like Matt said it is better for your engine to leave it on but he may have thought you meant your main air filter system by the look of his answer.....
That one you speak of before the main air filter i have taken off and gained no noticable performance but i have gained better fuel economy....
I have only taken mine off because sometimes when the rivers are up my engine is totally submerged for up to 1minute and i am worried about the exit of that hiclone thingy taking in water....