Ok, I have an S5 and it is having some annoying bogging problems. The car idles fine at 800rpm as long as it is sitting in neutral with no brakes applied. as soon as you step on the brake, turn on the heater, or turn on the lights the idle bogs to about 600rpm and then bounces between 900 and 600rpm.

I searched and found people talking about cleaning the BAC valve and I did that with no avail.

I can hear a sucking noise under the hood coming from around the intake manifold on the drivers side. I found a open bolt hole on the block that you can see between the main runners where the upper and mid pieces of the intake manifold connect, just a bit further in than the oil fill hole.

Can someone tell me if there is supposed to be an open hole there or is there a common vacuum line that causes these problems.