what are the main components in a muffler? is it fiber glass thread packed or is it just hollow. where can i get the perforated tube in side mufflers?

You can make a muffler yourself rather easily if you wanted to. You can get a stock muffler from your car and cut it open in half. rip out all the baffling and get a perforated or baffled tube and lay it from one hole to the other hole. Have it welded in place and then weld the casing back together. It will be pretty loud.

I believe the shit inside a muffler is kinda of like the fiberglass insulation you find in houses. BUT Im not positive. I just know you can make a loud ass muffler by doing the above

What do you have in mind? Why not just buy a muffler?

well i just found a place that does custom mufflers. but what i want to do is have a pretty much stock size muffler but i plan to convert the exhaust piping back to true dual like it should be. have the pipes piped like stock then going to a muffler that has two inlet/outlets that are straight shot. so that it goes through one muffler but stays true dual exhaust. plus this way it isnt anything fancy and too much after market looking but deffinatley makes a diff in sound and performance.

What makes you think that it should be true duel? Another thing, If I'm reading this right, you plan to run duel pipes to one muffler. You are planning on opening up the exhaust, only to restrict it again at the muffler. Maybe I'm missing something in your design.

the muffler will have two inlets and two outlets. it will be a straight through design. neither pipe will meet the other except at the muffler at which point it will be one case but two pipes going through the case.

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like this^.