I am looking for a cat-back system for a 1990 NA convertible. I need to know what systems will fit this application..

1. Are S4 and S5 cat-back exhaust systems interchangeable?

2. Are coupe and convertible cat-back exhaust systems interchangeable?

 

the coupe and vert ar interchangable, i used the full racing beat system for my last two 7's with one having the hks mufflers which was loud, but not that bad and now i have racing beat mufflers on the system and it sounds great and this system was straight bolt on, took me and buddy about 2 hours to remove old mufflers etc and install the new one. Also having owned both series and 5, the mufflers with be able to mix and match from cat back, you might need pipe from them to y pipe then mufflers but that will depend on what system you get, only if you remove the cats is there a differnce on the two, series four need to remove air pump and block it off. Hope this helps

 

cat backs are interchangeable on all models

 

I appreciate you taking the time to answer my question.