The magnaflows I bought were straight through, you can see through them, but the pipe wall is
perforated and wrapped in fiberglass I think. The magnaflow I bought sounded great, but I was
drawing too much attention to myself, and wanted to be a little more stealthy. The Super Turbos
are not straight through, but are known for very little back pressure, and much quieter, and are about
$50 a pop at Summit. They key to making power is a properly designed header, then as little back pressure as possible after the header.
the Dynomax VT below reminds me of my Magnaflow straight throughs:
http://www.dynomax.com/sounds-of-dynomax/And trust me, the Super Turbos on my Cuda above 5000 rpm are very loud!
I originally put Flowmasters on my Cuda, the sound was torture!