Ive been doing a little research into this tonight after an intresting conversation with the design engineer at blueflame exhausts and I'm gonna stand by what I said earlyer. Its the amount of precious metals in the cat that do the converting that matter, measured in grams per cubic foot, on top of the total surface area of course.
Taken from Milltech site: -
"It is normal practice in Europe to use much higher quantities of precious metals on catalysts, because European gasoline has more impurities in it which gradually poison catalysts. The Platinum and Rhodium in our cats are applied at a rate of 25 grams per cubic foot, which compares with between 5 and 10 grams per cubic foot for typical US aftermarket items"
Basically the cheaper sports cats skimp on the precious metal, thats how they cost so little and why they are more likely to throw up an eml. If you reduce the amount of cells and thus the surface area you really need to step right up the amount of material that actually does the converting. The chap at blueflame recomended at least 25grams per foot. There cats are loaded at 30grams per foot and cost £300.... You can draw your own conclusions about what an ebay cat might contain. Please dont think I'm being a bit of a negative bugger, I'm just trying to help. I just hope you dont have any problems.