Hallo Navin, welcome to car heaven. The E46 is in my opinion THE BEST N/A 6 cylinder of all times.
An open cone filter is on it's own not ideal, but included into for example a Rob Green Motorsport cold air induction kit which includes an oversise air mass meter tube, will make a difference for sure.
It' not how much you will gain with such a filter or CAI kit, but the combination of a few mods such as: CAI kit, properly designed exhaust system, Dastek Unichip conversion, shorter diff ratio, brakes, suspension,etc.etc.
What is important though, is to get proper training to be able to extract every bit of potensial designed into the car. You will wet yourself if you know and experience what the car is capable of. Do not drive fast on any section of road befor you are really capable to handle the car properly, especialy with DSC deactivated, around a bend or corner in 1st or 2nd with the right foot planted!!:fencelook:
Don't allow the clutch to wear out to the limit if it's an SMG.
Go for it, enjoy the car!!!:thumbs: