I've been having a rough high/idle and weak braking for a couple weeks now. I attributed it to a dirty IM because of a dead O2 sensor (running rich for a week). Anyhow I was doing an induction cleaning this morning and saw 2 bolts on my upper IM rattling around (also heard a sucking noise). Pretty stupid of me for not checking but between the seafoam cleaning and the tightening up the IM everything is back to normal. So just an FYI check your IM bolts once and a while. I had them torqued back down to spec with blue locktite after my HG job but it still worked loose.

 

I had something very similar happen- a few days ago I had the ever so slightest amount of coolant sitting in the valley pan. And I thought, man, I just replaced the IM gasket like 5 or 6 months ago. Thought maybe I did it wrong.

Come to find out, half(or more) bolts were loose. After being torqued,with locktite. And some of them are a PAIN to get to with everything in place.

Guess I'll have to add that to my list of things to check at every oil change