There are 3 hoses and a tube. No Flame Trap exists. Two hoses are accessible from the top of the engine. The one located by the sensor last intake passenger side and the one near the oil cap.

When I removed everything the area where the most crud built up was in the tube which connects from the bottom of the oil trap to the block. This tube is a replacement item along with the tube by the sensor. Of course the whole trap is also replaced.

There is one more tube which is part of the oil trap itself. This goes into the top of the block. You can't get at it, however once you get an oil trap you'll see what I mean. I believe either fcp or ipd have a picture of the trap on their site.

To identify it, The trap has a round piece (like one mickey ear) on the top left side).

I don't think spraying will work but you can give it a try. Some one on Volvo-Forums said that there is a diaphragm in the trap that goes bad. Possibly this accounts for the whistling.

Good Luck