Aos?

[Squozen]

It's due to be replaced as a preventative measure anyway. Go for it.

The rough idle with the oil cap off is completely normal, though. I'd be more inclined to suspect your MAF given the lack of smoke.

[Frodo]

Yeah, I figured the MAF should probably be cleaned at a minimum. I haven't checked my air filter for awhile---that probably needs to be done as well.

I also was pretty sure that, mileage-wise, this is about when the AOS tends to go and (despite the gorgeous Boxster-friendly weather we're finally getting in NE Ohio) was just worried about driving it with what I thought might be AOS-related signs.

I've had the oil fill cap off in the past (when idling). But I don't remember how much (if any) suction I heard/felt back when I'm sure the AOS was fine. Should there be some? A little? None? I'm assuming it's best not to push the AOS to the point where enough oil gets sucked into the intake to create the tell-tale sign of huge amounts of smoke coming out the back.

I wanted to re-read Jake's write-up on the different modes of failure of the AOS (smokey vs hydrolock, etc) but have had trouble finding it...