Where can I buy one of these
 

https://www.miataturbo.net/picture.p...pictureid=1089

It's some sort of WG exhaust seperator

One came with a cheap turbine outlet tube I ordered off of eBay for my old SRed S14... Not sure where to get one by itself though.

cut a piece of pipe out?

Get a bell mouth downpipe and dont worry about it anymore :)

+1

Piece of pipe 1/3 diameter, and a quick weld job. Profit.

My shit is already on the car. I'm not messing around with pulling everyhting off. Plus, my DP has two nice threaded holes for one of these.

Well something is going to have to come off to get it on there anyway. I don't know how much luck you will have at finding one, at least one that will fit correctly without slight modification. I still say get someone to fabricate you one if you want it so badly. Otherwise, good luck.

You can get them with an sr20 elbow on ebay for 60 bucks. I can get one on by disconnecting my dp from the turbo without removing it from the car.

Getting one machined will probably cost more than $60. Is the performance gain worth the cost?

I have a nice DP
https://www.miataturbo.net/picture.p...pictureid=1046

You may can slide it in there without removing the DP, but can you get it far enough out of the way to get a wrench on the bolts that hold the separator in place? Maybe it will drop down far enough.

Block of steal drill 2 holes grind to shape. Done

I wouldn't recommend stealing a drill for this project. Or two holes grinding for that matter, at least ass to ass.