FJRiders.com

Turns out the thermostat wasn't leaking, but a hose was... badly. Valves were in spec... Will post readings later. Dealer went through front to back... plugs, oil, tbs cleaned, final drive, air filter, etc. Still runs like crap cold but ran great once I had been on the highway for a few.

I've ridden in the cold many times - into the low 30s. But never cold at a high altitude. Could that be the magic combination that causes it to run rough/die easy when cod?