I didn't notice any loss in top end and did gain a little low and mid range on my 400 hp 365" SB. I'm using a deep port matched mopar intake with the DC mechanical 6 pack. I can actually flat out floor it and open all 6 barrels at once and it goes like it was shoot out of a canon !! It does have a 4,400 rpm stall with drag radials. Plus the WOW factor over the single 4 bbl is worth it IMHO.