I'g putting the engine tins back on getting ready to put the engine back in the car. I have this gasket that I don't know where it goes or what it is. Any ideas?

Hard to see scale from the photos. Looks like seal between engine tin and oil cooler to me.

Yep, looks like the tin to cooler seal, 411813215A

This one.

I have new ones 10.88 that fit better than OEM in silicone. definitely a needed part

https://900designs-container.zoeysite.com/o...nd-tin-gasket-1

Awesome. Thanks for all the help everyone
. I'll pull the tins back off to install that.

All your seals like this one are important as the T4 runs somewhat hot anyway,every bit makes a difference,clean crankcase,cooler,and good engine bay seals and correct working thermostat go a long way to making it a motor that will do large miles after a correct rebuild.
Good luck.