I know how a catalytic converter works. Yes it does restrict some exhaust flow but if you use a highflow cat, it shouldn't be a problem. There is a reason why they fit the cats. To save the earth. The cat has crystals that after heating up burn out much of the harmful gasses in the exhaust thus giving you cleaner emissions.
If you have a highflow brand new catalytic converter, the max drop on u'r power wud be about 2bhp! this is a small price to pay to save the earth. But again ... you might call that stupid if u don't think on those lines.
The only time when cats actully restrict the exhaust a lot is when they become old and clogged. Otherwise they don't hinder the exhaust much.
Also, I don't think you could gain 50 bhp by just removing a catalytic converter! ... I mean do u know how much 50 hp is?? and just with a cat??? right!!!
The only way this could happen is if the cat is COMPLETLY blocked and the exhaust is passing through like 1cm of opening instead of 3 inches! but then again if it were blocked that severely u'r car wudn't start up in the first place! 50 hp by removing a cat! I wud kill to see that happening!