Just to add some clarity. First, and foremost, why we offer catted downpipes, and primarily recommend them are for a number of reasons. #1 smell. I don't know anyone that would want to deal with the stench of a non-catted setup on anything, but especially cars and trucks as nice as this. #2 at least there is some improvement in emissions vs. non-cats, even though it's for race use, it's not a bad thing to make it cleaner than no cats would do. #3 raspiness, cats do help with the tone of the exhaust. #4 the power difference is not what most people think. While there is an improvement from downpipes in power, a high flow race cat vs. no cat is only about 2-3hp difference on builds exceeding 700hp. So, it's a fallacy that ditching cats vs. a race cat is going to unlock power. It's lucky to be 2hp on anything EcoBoost. #5 oil smoke, ecoboost vehicles have a high tendency to have some amount of oil smoke, even when stock, but by ditching cats entirely, this almost becomes a guarantee that it will have oil smoke.
Now, as for running a different cat, now you have a tradeoff. For a catalyst to be better at it's job, there are a number of things that much be true. #1 is it will be more restrictive. This means it will be more restrictive than a comparable cat that is less effective. To offset this, you can make the cat larger, but we're talking substantially so. It's not linear, meaning a 50% reduction in flow through the brick does not mean you increase it 50% to offset the loss in flow, a good baseline is doubling it in size to get back to your starting point. But, since this would be an exceptionally expensive catalyst assembly, no one does that, so, instead, they accept a reduction in flow to achieve this efficiency in conversion of emissions. So, you've now put a downpipe on the car to gain flow, but then put a cat on it that flows similar to stock for the chance of not setting a light.
