The FSM calls it a Switching actuator. Looks like some sort of vac operated actuator that moves a flap covering 1/2 of the exhaust.

What i the point of it? Anyone remove it?

 

Twin scroll acuator, search for it. In sort it closes one runner for the turbo to help spool it up in low rpm situations, to help improve "city" and economy driving. You can remove it, make sure the flapper door in the manifold is removed, only downside i can think of is spool will be slower

 

Thanks. I will keep it then. the faster the spool the better

 

Oh also-

is there a diffence inbetween the s4 and s5 radio surround besides the length for the radio?
I have a good s5 factory cd player i want to make fit in a s4

I went through the wiring and i have a s5 harness that will plug up to the radio and i can splice it into my destroyed harness....

 

s4 is plastic and s5 is rubber.
the s4 has the vents and A/C control trim incorporated together.while the S5 has a rounded vent separate from the A/c Controls.
really the S5 is better as it will take a bit of wear and tear, while the s4's tend to break...get the S5 shifter surround too,as it is rubberized outside too.

 

The s4 and s5 vents aren't interchangeable though so you need to match series between the vents and radio surround.