Does the tubing go from the engine inside, (emissions tubing) go through the firewall into the center of the dash somewhere? It seems like a mess, and I'm not sure how deep to think about going? I know the vents seemed to stop working around the same time the "check engine" light went on, and leaks started happening. The idle is a little funky, and it doesn't have the usual power it should. When an underpowered car gets even slower, it's not much fun... Are those tubes all connected?

Here is some help with the hose I think you're describing-vac hose:

http://volvo2.homestead.com/Ventwierdness.html

Also, if your check valve isn't working I recently saw a post in which Art said to wash it out.

Travis

There is a vac line that goes into the cabin through a check valve. It ends at a reservoir and then the entire vent door control system is powered by it.

That tube is not really big enough to effect much more than the stability of your idle if it is disconnected.

Any chance that during some prior work you connected the Flame Trap up to the wrong nipple...possibly swapping the two lines.

Mike