I am planning on getting my exhaust done at a shop (have the muffler, need to take it to a shop). I have an s4 and want to stay with the primitive s4 actuation method while getting the benefits of an improved exhaust. I was thinking about removing the precat, keeping the stock main cat and going single drivers side exhaust. Will the aux ports still function well (I know where in the band they actuate will change but will it be reasonable?) How does this effect where in the band it actuates, is it earlier or later? Thank you in advance.

 

If they open at all, they'd open later and probly not all the way.

 

Why not just buy an exhaust made for it? Like a RB Header/Presilencer and then go custom on the cat-back. You seem to want an improved exhaust but for some reason you're keeping a 20 year old converter.

 

Or if your dead set on your exhaust, go to an electric port actuator.

 

The stock exhaust is the optimum exhaust for the S4 port activation system. Second best would be a specially made one like the RB unit.

 

aux ports should still work with your set up as suggested as long as they were working before.