blslhi

Also I noticed that my stock accordian hose has a hard plastic hose connected on the bottom facing the firewall, where does that plug go to when you use the RS4 accordian hose, as it has no connection for that hose?

davenew

The cars that come with the airbox flap have an extra solenoid controlled by the engine computer. I tried connecting the hose to the hose that goes down to the turbo inlets. Those hoses only generate enough vacuum at wide open throttle to open the flap around 75%.

I ended up removing the two screws that hold the flap actuator to the airbox, pulled it back so the flap is always open, and installed one screw to secure it in the open position.

In other words, the actuator is only held in place with one screw, in the wrong hole. I stuck the other screw in the un-used hole so it didn't get lost.

I measured a max vacuum of around 12 inches of water at WOT (in the airbox, below the filter) with the flap closed. With the flap locked open the max restriction went down to around 2-3 inches of water.

After all of that, I ended up cutting a hole and attaching a 4 inch bellmouth intake into the bottom half of the stock airbox. It fits to the top half of the RS4 box. I hear much more engine hissing noise with the big bellmouth hole. The RS4 airbox w/flap open is probably good enough and prevents the noises.

I help with the accordian hose. My car is too old to have it.