These are the most common sizes and shapes of the XR-1 mufflers. The oval is the most popular for street cars because it doesn't hang down as far as the others and has more packing material. After all ...
Drag racers who use Borla's XR-1 stainless-steel racing muffler can now make some extra cash when they win, thanks to a $315,400 contingency award posted by Borla Performance for the '94 NHRA season.
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