Previa:
Glass-packs are very cheap, loud (when used by themselves), small diameter mufflers. Sound deadening results from the fact that they are filled with fiberglass mat, around a perforated pipe, inside a larger round pipe/housing. But they probably muffle more than a resonator! They tend to remove the "harshness" from the exhaust note.
Look at Summitracing.com, and search for "glasspack".
If you buy one, be sure to look through the core of the muffler before you purchase it - most of the cheaper ones have a core that is 2" dia, regardless of the the diameter of the inlet/outlet - and you don't want that... And the higher quality ones are now packed with stainless steel wool, not fiberglass. The fiberglass tends to break down over time, and cause the muffler to get louder, as it ages.
My HZJ was inspected before I modified it, but it is now quieter than stock with the two mufflers... Most people remark at how quiet the LC is, particularly when it is going down the road.
Being in the Interior, we don't have the air-care inspections to contend with. I would guess that it would not affect the inspection, but I cannot say for sure.
HTH's
Jim.
(PS - the best way to muffle the 1HZ is to put a turbo on it!!!)
