Hello, i own a 99 audi a4 quattro 1.8T and looking to take out stock muffler for a FlowMaster but not sure on the size of my Inlet/Outlet..2.25"? 3'? 2.5?.. also i am looking for a deep tone sound so would you recommend the Super 44 series or Super 10 series for aggressive tone? can someone help me out?

 

I believe it's 2" (I just had my 2001.5 A4 done and it was 2"). Some say 2.5", but I'm not sure. Your setup might be different than mine.

With Flowmaster mufflers (which I've had a lot of). The lower the series, the louder the muffler.

Personally, I think an extra loud Flowmaster would sound like ****.....and even if you insist on getting one and you really do want that super-deep sound, you're going to have to get rid of the huge resonator under the mid-section of the car, and get high flow cats too.

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I have the standard factory cats installed on a 3'inch stainless steel cat-back exhaust system.

I never messed with high-flow cats, but if you can pass emissions with them, why not get them.

The diameter of the factory exhaust pipe is 2.25 inches, or 2 1/4.

 

Magnaflow 14815 and a vibrant res to replace the res under the mid section of the car. Not terrible loud (sounds like a hybrid after i get out of my straighpiped s4 haha) but it does sound great.