I still wouldn't really go w/ the 50 shot, while 50 shot is safe for the internals and not blowing it up, the tune will have little to nothing to do w/ how much gunk ur gonna build up in the cat. you can do it, but it will shorten the life of the cat!!
it will work 1000x better if you don't have a cat, then you don't have to worry about it!! if you really are worried, when you have to check emissions, just take the header off and put the manifold/cat back on!!