The exhaust leak sound you are hearing is coming from the AIR pump. It runs when the car is cold, after the car warms up it turns of automaticlly. The Air pump is part of the emissions control system.
__________________ 02 Z-28, A4, 2:73 rear, 13.20X @ 108.XXX mph 2.2XX 60 ft, free mods, 160 thermo, gutted cats, cut out, p&p throttle body, K&N filter, hp tuners, Racetronix P&P fuel pump kit, TR55 plugs, home made turbo kit w/fmic and meth kit coming soon,everything else stock, for now  . |