While the Squires system is a great idea and is capable of making great power, the guy you talked to has no clue what he's talking about. Regardless of whether an engine has a turbo or s/c on it, better flowing exhaust will allow for more power to be made. Its actually MORE critical with a turbo than s/c, but will benefit either system. Just wondering, what was it that convinced you to go turbo for this application instead of a positive displacement s/c (Eaton, Kenne Bell, Magnacharger, Whipple). Did you really take a good look at the dyno results? Are you only interested in a peak number, or do you really want to get up and go? A 4.8 needs all the help it can get to be fun on the street. Anyway, I have seen the STS in person, its nice, complete and works well. See if you can find someone with a vehicle like yours to go ride in.