There are different scorpions. U can tell if it's restirctive by shining a torch down the tailpipe. U can see that on some the bore size drops considerably - they are worse than a std system. A std system doen't pose a restriction at 200hp - maybe higher but ive not tested it.

The best off the shelf system IMO is the 3inch bore Magnex, with3.5 inch tailpipe. It's quieter than most systems, and being a 3inch bore, good for power.

My favourite zorst is the Power Engineering item in my Avatar. They are VERY VERY quiet at mway speeds - just what i like, but others dont. It burbles nice on idle, is incredibly well made, and looks the bollocks.