No gasket, when I rebuilt my turbo, I took apart 3 turbos before I got one with no cracks in the hot side, and none of them had gaskets there:)

nope, no gasket

https://cimg8.ibsrv.net/gimg/www.rx7...d3eb84b6f4.jpg

Am I wrong, or is that part of a gasket hanging between the plate and turbo there?

I see it now... the plate is behind that vac line. thats the down pipe

you can try this stuff. SPA Turbo USA Gasket Eliminator and Flange Sealant | Exhaust Header Wrap and Thermal Performance Products | Design Engineering, Inc.
It actually worked with our time attack car.

What's it's thermal threshold? Did I somehow miss it?

I looked and couldn't find it either. The only thing I found was were it said to call a number to get the specs on it.... Shitty way to sell a product if you ask me.

I called DEI this morning and asked about the spec for the material. Once cured it is rated to 1200 F continuously and short term spikes (typically meaning less than 5% of total time) to 1600 F.

Permatex Red is only rated to 650 F intermittent and Ultra Copper is only rated to 700 F intermittent. They do not state a continuous rated max temp for either material.

Sorry for the late response. I don't have actual numbers, but the car we run is a high compression, 11.5:1, gtx3582r around 650whp cyl engine with professional drivers beating the crap out of the car. It's even been too road Atlanta which we were able to reach over 160mph on the back straight. Of course time attack cats only run 15 minute seasons though.

The stuff has held up for 2 maybe 3 time attack events. We have not run it in overt a year. This was the first car we tried it on. I bought it to use for a gasket from the turbo outlet plate. I custom made a downpipe that replaces that part. After talking with bluet2, I ended up making my own stainless steel triple layer gasket. I want sure how straight my flange was even after belt sanding it, so I added this sealant as well

that would probably work, EGT on the stock ecu is around 1300F peak, the turbo would be somewhat colder. an aftermarket ecu tune would be more like 1600F peak, and so it wouldn't last as long