i'm new to the evo community and i don't even own an evo yet hahaha, but i'm a subaru owner with aspirations of owning an evo in the near future, i'm trying every dealer i know to get one. i posted my question in the noob area but it seems that none of the "veterans" of the evo game go in there and offer help so i'll post it here where hopefully it'll get more publicity.

what's the difference between an o2 dump from an ewg? i know you need to be tuned for the ewg but what about the o2 dump? and is there any performance gain at all from the o2 dump? thanks in advance

 

You should tune the car for any performance upgrade if you want to extract the most performance out of it. People have used an EWG on the stock turbo's with quite a bit of effort, but it's not worth it in my opinion. An 02 dump works pretty well, easier to install and a much cheaper to buy as well. Depending on brand and tune, people have seen 15whp with just the install of an o2 dump. And I believe that's not over stock, but over an aftermarket, recirculated 02 housing.

If you do some searching, you'll find a lot of answers. 02 dumps have been discussed like crazy here.