I just received my collected RB header a few days ago. i was reading the instructions they gave, and the only thing i am confused with is the fact that it says on S4s you need to remove the ACV (they included a nice little blockoff plate with the header).

now, currently my car is a Series 5, with a Series 4 engine (the shortblock). The entire intake manifold is Series 5, as is the ACV. do i still need to remove the ACV? also,

- Why does the ACV need to be removed in the first place? clearance?

- If i remove the ACV on my S5, i am assuming the solenoids still need to be hooked up otherwise i will get CEL codes? there will probably have to be some sort of vacuum line rerouting also (oh joy...).

 

ACV is removed because without a cat, it's worthless on an S4. You'll need it on an S5 for VDI.

That's about all I can help you with.