Downpipe Decisions

Hello all, I am looking into purchasing a DP! I've been reading a lot, have seen a lot of reviews, and now I just have a few final questions before making the purchase.

I am pretty decided on Invidia. Good price, and from what I've read good quality. Supposedly the wastegate interference issue has been resolved, and that was the only negative I heard about.

Catted or Catless? Is this decision pretty much based on having a legal exhaust system or not? Since my county has no emissions/inspections at all, and is a very rural area, I am not worried about that. I just want to clarify that the only reason for both options is for emissions/laws. The Catless should obviously yield higher HP, even if only a little, than the a catted. Just common sense, right?

Also, most downpipes that I have seen and read about have been advertised as 3" inlet at the turbo, and no information about an outlet diameter. So far, I have only heard that Cobb steps down to 2.5" at the outlet.... So my question is, if I am keeping my stock exhaust set-up aside from the DP, will I need a size adapter between the downpipe and stock exhaust? I read somewhere on the forums about a flanged/bolt-on step down for between the two pipes, maybe Grimmspeed? Not a deal breaker if I need to modify it a bit, I would just like to know what I'm getting into.

Thanks in advance for the help!

Honestly catless is always going to be cheaper and catted will help kind of save the environment, as if anyone else is even trying anyways. Pick whatever fits your budget.

As for the outlet flange, the Invidia should also be a 3". I believe someone makes a gasket thing that bolts up to 3" and tapers to 2.5" so you can bolt it to your stock exhaust.

Hope that helps! By the way, I'm switching from catted to catless.. Only because I have a buyer for my catted DP, need a better tune, and figured why not lol.