I've got the Systemax on a 331, e85, GTK850 (72mm/.81AR) and the torque curve is insane down from about 3000-3200 all the way to 6200-6500. The car weighs 3540 with me in it. It's not the fastest or quickest but a 10.38 @ 134.2 is tons of fun. Oh, it's also an auto (built C6). I've got a lot of tuning to do and a trans brake to install. It's currently leaving of the foot brake. On the street, from 3000-5000/5500, it's stupid fun. On the track, crazy, addictive, fun.
A friend has the Victor jr w/elbow on a carb style throttle body on a 347 w/42 lbs injectors. He uses an On 3 turbo kit (76 or 78mm) and T-56. According to him, his car gets going at around 4500-4800. So, on the street, eh, not to much excitement. On the track, fun.
Another friend has the Victor efi on his 306, 76mm, 190 T.W. and it gets going around 4500 but the power is unreal all the way to shift point. On 21 lbs, his 3770 lbs. car traps 142 mph. 35 of them after the 1/8. He says it's more for racing than street.
Hope it helps!