Found this quote....
"According to engine builder Mike Osucha, (MORE Performance, Charlotte, NC) "We recently built a 396-cubic inch LT1 engine that produced 455 horsepower with an open exhaust system. When we installed two Random Tech converters, the engine produced 458 horsepower. When you look at the complete test results, you see that at some points the engine makes more power without converters than with them. And vice versa. I think the bottom line is that there's a tuning effect when a slight restriction is placed in an exhaust system. But the real point is that with the right catalytic converters, you don't have to sacrifice any horsepower to make an engine emissions legal."
Found it here....
http://www.randomtechnology.com/technical.html
This would be the only company i would ( and have ) buy from.
But do lot list a PT number yet but can match one to the PT. here ais the page...
http://www.randomtechnology.com/solidtest/8000.htm