35th camaro

how much air can the stock air box flow on 2002 ss with 402, just seems the small opening is not big enough, couple years back i opened the bottom of the air box to get more flow, but i am reliezing that my iat have gone way way up and my car runs like **** after being stoped in trafic, i am going to make a little extention of ducting like slp has,or block the hole like stock again, what has been your experience? also do not want to make any obstruction for radiator.