on a stock smallblock with a stock cam, it's easy to see 500-600hp crank HP out of a well designed turbokit.
Once I hear a cam, i know they've fiddled with the longblock, and if they've fiddled with that, chances are the mods go more than skin deep.
That's just how I see it.
On the other hand, a Supra that idles at 1000 can sound just like any inline 6 with a fart can. Meanwhile, the higher idle can smooth out the lumpy sound of larger cams... so that you have a car that looks lightly modded that can still do this:
http://members.cox.net/dblegle1/Supra.wmv