SRT-6/AMG C32 air boxes (big post with part numbers and prices somewhere on the forum).

Nitrous system operated by a TPS monitoring system (look at the zex TPS monitor, this is to keep it from spraying when active stability management kicks in).

as others mentioned ... magnaflow exhaust system + SI tune (careful mixing this with the nitrous as advanced timing and nitrous only mix if tuned very very well and shot is kept low).