Well I had my 123 up on the lift ,slapping in new motor mounts and rechecking every thing after my trans swap aaannnnd I started looking at that ole rusty muffler and well before I knew it, about 2/3 of the tail pipe was laying on the ground.A quick trip to the parts store for some clamps and a chrome tip, I had my strait pipe dumping out right in front of my right rear tire. There was a noticable difference in acceleration. This along with my new/old manuel trans is making the little car fun to drive.
It wasnt as loud as I thought it would be ,but It doesnt sound too bad.

Straight pipes rock
Having it stick out past the body helps make it quiet

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Well, you must have a turbo eating most of the noise. When the muffler fell off my 240TD it was louder than a Mack truck.

Turbo > muffler

Yes, the turbo is a restriction which makes it a good muffler.