don't really want to shell out for ppp so have just bought 2nd hand wr sport back box. for ppp, don't they also change the section labeled 'cat pipe' in the diagram below?

seen these 'cat pipes' (genuine prodrive decat's) advertised, so can they simply be bolted on (know they have to have provision for 02 sensor) or do you have to adjust anything else e.g ecu?

as all subaru parts would be used then warranty should be ok?

 

from what i understood it was the center section that was changed - its not a cat, its a just a noise resonator as no sensor plugs into it.
Removing the CATs on these newages can be a tricky affair. I've read allsorts on here about detonation being an issue (ECU confusion leading to missfueling situations etc) when you put a clean pipe in place of the CAT.

ask your dealer about the warranty and utilising alternative scooby parts. I reckon you should be ok with a sport backbox as like you said its a Subaru part.

Frank

 

Changing just the back box should be allright, but not the rest. Best is to ask your local garage