The Magnaflow problem "may" be only with the larger 24" model that is offset.
For some ignorant reason they use a 2 piece perforated tube inside and it is simply a design flaw because that one WILL start to rattle and fall apart.
IF the 18" uses a 1 piece tube then it may be just fine.
I wanted quiet so after the Magnaflow sadness I went with a Borla 40665 Turbo XL which is great.
Cost is $102 on Amazon right now, usual price is around $168
Amazon.com: Borla 40665 Turbo XL Center/Offset Universal Performance Muffler: Automotive