I popped the hood and blipped the throttle, and this horrible knocking noise was coming from the engine
... Oh @#$%, I said... Please, for the love of God, anything but that!!!I took it to work very slowly, and asked a tech what was going on, he heard it and developed an upset look on his face, which was very quickly transferred to my own face, I said "Please, don't tell me, it can't be"... He said "Yup, I think it is"...
I was thinking to myself, this is impossible, I don't abuse my car, I change the oil frequently, and I use a heavy enough oil, plus this is a Subaru EJ22, one of the toughest engines I've ever seen... I can't be throwing a rod!!!
But the actual engine builder came and listened to it, and he said 1) this engine is running way too good to be getting ready to throw a rod, and 2) the knocking is not constant, only after judicious throttle application and then a few seconds after until it idles again...
He concluded that my water pump has called it quits, which is not really worrisome for me because I'm gonna replace my timing belt very soon anyway, and replacing a water pump is far cheaper than an engine rebuild!
it may clear things up... and if not, you get to blow steam/smoke all over the place...