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Old 11-04-2009, 03:51 PM   #12 (permalink)
ncs
EcoModding Lurker
 
Join Date: Jul 2008
Location: Idaho
Posts: 45

RockMagnet - '04 Subaru Impreza wagon WRX
90 day: 26.16 mpg (US)
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Sport Compact Car magazine(rip) published some aftermarket cat test results a few years ago. Power losses were something like 1 hp per 100hp produced. The aftermarket cats didn't clean as well as the factory ones, but they did well enough to pass the tailpipe part of California's emission test. There is no excuse anymore not to run a cat.
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