...in the range of 340 to 370 whp. That's pretty much with all bolt ons and stocker turbos. Sport 500's will most likely(re: your Z tuned properly) get over 400 whp with 425 to 440 whp not out of the question! E-mail Mark Leader in SoCal(tt.net name: SirpriZ) for more info. He has Sport 500's....Others here do as well....