RR69

I was wondering if anyone is running one of those hi-flow Metallic substrate converters? I like the fact that they are are metal and they are suppose to flow pretty good. I read in MMFF they flow almost as good as the high one the the highest flowing catalyst cats. But will this metallic cats last longer and will the pass the sniff test? If not what are the best hi-flow cats that will pass the sniff test and last the longest? I read somewhere that aftermarket cats only last a matter of years, is that true? Thanks Matt, oh yeah this if for my basically stock 93 lx 5.0 5sp