I fitted a proper rear muffler and a resonator.
Aftermarket manifold, aftermarket dump, hi flow cat, aftermarket resonator, trust muffler.
Bobs yer uncle.
Unless you want a loud car, in which case just put the stock back on for engineers.
If you want to keep your rear muffler fit the quietest biggest most high flowing middle muffler you can find.. $100 installed or less - that'll keep the note just not as loud (I like the sounds you get from a big big middle muffler and cannon style rear).