From what I understand, these engines typically need new head gaskets after 120k or so. Apparently, because this is a hybrid, the engine turns on and off more frequently than a typical engine and this causes more heating and cooling of the engine block and head, which stresses the gaskets. I had the same symptom, got the head gasket replaced (a mobile service here in the SF Bay Area) and have had no problems since. (Look up GasketMasters on YouTube and there are a few videos showing how you can do it yourself - search for Prius, since that's the same engine. They also have videos explaining why this tends to happen.)Bad news , shakes are back. Now I’m thinking bad head gasket . Maybe due to me driving it on only 2 coils .. maybe. It’s has 129k miles on it so maybe it’s just time for new gasket anyway. Will post after I get work done what the outcome is...