i know that the s4 needs the backpressure from the cats for the 5th and 6th ports, but what if i get a straight pipe with a resonator test pipe. Could i use that to replace the cats and would it create enough backpressure for the ports?

 

You need the tube coming off the cat (or something similar) to get the pressure to the aux ports to open them. A test pipe will not have this, and even if it did you prob wouldnt have enough backpressure to operate them. There is a fairly simple writeup on how to electronically operate them, I think in the archives.

 

^correct or you could get the precilencer from racing beat for the s4 which has that tube on it. they flow really good, i have one on my s5 and it made a huge difference in power (i also got their cat delete for the 2 precats)

 

what if i just gutt out the cats, would i still get the power and the backpressure needed?