Let's see what the experts say(because I'm not one).
I didn't re-read everything on this thread, but I did go back and re-read the original post.
If this is the one and only time, I think I'd just drain enough out to get it to where it should be and not worry about it too much. If it happened to be enough to make a serious pool in the intake box, then that might be another story. I know you said you had some in there, so I guess I'd just drain some, clean the box up, maybe the air filter(depending), then maybe carefully wipe the throttle body area as much as you can and call it a day.

 

If both of these statements are true, then they didn't cause the oil found in the air intake.
Every RX-8 that's had their oil changed at the dealership would have malfunctioning air intakes then. And they don't.

 

I doubt they have serviced an S2 before tho. there arent many rx-8's where I live.
im keeping track on how much they overfilled, its been 360 miles and its still 0.5cm higher than the full hole. so its about 0.5quart more than what they shouldve put in.