I also have a SLT with the single side exit exhaust. Past weekend I installed the mufflex 18 inch system. Install was pretty easy, only took about an hour and the fit was perfect. Nice deep rumble, but not too loud in the cab. You can hear it well when accellerating though, very nice tone. Very pleased overall.

 

i went with borla...

i have a video on this forum... do a search.. u might like it

 

I have the single pipe with the mufflex. I wrote a pretty thorough review in the FAQ section.