So my 1987 has just started doing something new I've never dealt with. 
It starts and runs but about 2 minutes into a drive it feels like its running out of gas. Power drops, throttle becomes unresponsive, etc. then it dies. 

If I go to fire it back up it will crank and will even catch and want to run but dies within a second or two. Every try, same result. 
If I let it cool down for a bit, say 15 minutes or so (as I type this) it will start and run fine until I get home. 
It does it just as the thermostat opens. 

I have tried unplugging the oxygen sensor and no difference. 
Is this perhaps the fabled vanagon syndrome or a failed temp2?

Thanks!

-craig