well i personally started with a header (found by accident at a junk yard on a scoupe before i knew about anyone else hoppin up hyundai's iwas the first in the area) fabricated the missing section of pipe with assorted exaughst peices from pepboys and came out with a sizeable jump in power then hacked off the muffler and added a cherry bomb glass pack and a resonated monza tip.
worked great and sounded great (LOUD AS HELL THOUGH) then after my fabricated mid pipe met with an unfortunate rock i replaced it with a 2" front to back exhaust and a bomz high flow muffler with a silencer....
after all that i would say if your gonna fabricate don't be cheap you will notice power gains either way but you'll notice the largest difference if you put more into it cuz it is true you get what ya pay for

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blue
4-door 2000 hyundai accent
backyard lowered 3"s
header and 2" exhuast bomz muffler
matrix air filter

Z3R0