Never really ran like it, though that might explain why the cooling system doesn’t quite keep up under hard driving.
Anyway, After reassembling the intake I hooked it up to my smoke test thingy. After noticing a loose vacuum hose, the real mystery came out: My intake plenum has four holes in it, clearly visible in this photo.
Not seeing them? That is because they are in the dumbest place possible.
Yup. Apparently the mounting tabs are “part of” the air system. And by that I mean looks like someone didn’t use quite enough plastic when they molded this part and the result is four small air leaks.
Short term I am going to fill the holes with shoe goo (or more likely Permatex Black) and send it. I might look for one that is in better shape than mine later on, but for now the quick fix should be fine.
The car ran fine before and those tabs have been like that as long as I’ve owned the car. Wonder what it will be like now?