Well, putting on a DP/MP isn't going to make the car smoke. The stock cats will just hide it. If the turbo seals are going bad, they are going bad. I was a bit worried it would start smoking after I put this on (my build date is 2/07) and then I would have to put the STOCK one back to on get warranty work. Sounded like a headache, because if I had the aftermarket parts they might refuse work, but then if I went back to stock they wouldn't be able to replicate the problem. BUT, this is a known issue by mazda, a few people have got it taken care of no problem. It's a little bit of a risk I guess, but I'd rather know now if I have leaky seals rather than later once my warranty is up or something.
Mid pipe by itself would work just fine, corksport used the stock style gaskets.
I'd recommend both DP and MP for power reasons (had just custom MP before this), but just having a Mid pipe would be nice if you have to pass emissions /warranty work etc.