Re: APR 2.5" Downpipe (Playa178)
You cannot see it, but on the "other" side are the two "bung" holes for the upstream and downstream O2 sensors. Anyhow... uhh... YES ... the downpipe includes a small "reducer" that is about 3 inches long that allows you to run the APR downpipe with the stock cat-back (or ANY aftermarket cat-back that is non-APR).
So, in answer to your questions, YES! Also, as you can see, the APR system, like the stock system, is one long downpipe that incorporates a higher flowing cat as well. The whole APR system works VERY nicely... cheers!