Regarding the OP question; I have used Goerlich XLerators on several cars over the years (my own and customer cars). I have only used them on '60s and '70s V8 applications.
They are VERY well built units with a deep tone. They flow much better than a turbo style muffler. They are a "straight-through" design, using a perforated stainless steel inner tube and densely packed (stainless steel and ceramic wool) case. They flow 96% to 99% of equivalent straight pipe flow rates.
Several videos on YouTube showing these on various cars, but primarily V8 muscle cars and late model trucks.
I know it doesn't help much, but here is a video of is how they sounded on my 71 GTO: YouTube - 71 GTO with Xlerator mufflers_0001.wmv
