98 Windstar 3.8L - Upper intake hose question

Hello,
On my 98 Windstar 3.8L the Upper intake air hose to brake booster feels to have pressure builtup inside and expands as a balloon somewhat.

Is it suppose to be under pressure or Vaccuum?
Please reply.
Thanks.
Jay

Mine acts the same when I manually tweak open the throttle plate. Slightly bulges at the Intake end. I'm not saying that it is supposed to as I'm currently trying to figure out an intermittent misfire situation and as far as I know it is supposed to be under vacuum.

*edit*
I encourage anybody with a 98 3.8L engine that is running well to test this for us. Pretty please? :)

Well, we all know the vacuum is (normally) the highest when the throttle is closed. On the chance that someone has changed out the hoses ... possibly to a thinner wall hose, that shows pressure differences more than the OEM ... or that the hoses are hooked to the wrong spot, here's a primer....'99 3.8:

There are three vacuum ports on the "backside" (engine RH) into the intake manifold spacer (between plastic upper and metal lower).
1) Toward the engine front, there is a port for feeding the vacuum controls inside cabin and elsewhere.
2) In the center, there is the port that feeds the vacuum booster.
3) At the rear, (near tranny) is the port that feeds vacuum regulator and control for EGR system.

Hopes this helps, but I've never yet noticed if the hoses flex or not.

Mine is only slightly visibly bulging. When I have my other hand on the hose I can definitely feel it expand slightly when I tweak the throttle plate.