More weight info for a 2011 STi Sedan:
Stock:
Header & Up-pipe = 26.5 lbs
Header Heatshields = 4.5 lbs
Downpipe (2 sections) = 18.0 lbs
Cat-back = 41.8 lbs (Mid/Y-pipe = 14.8 lbs, LH Can = 13.5 lbs, RH Can =13.5 lbs)
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Aftermarket:
Tomei Equal Length Header and Up-pipe (with Jet-Hot 2000 coating and 130 ft. DEI Titanium 1" wrap) = 23.8 lbs
Invidia downpipe with cat = 13.5 lbs
Invidia Q300 Cat-back = 57.0 lbs (Mid-pipe = 12.2 lbs, Y-pipe = 7.1 lbs, LH Can = 19.0 lbs, RH Can = 18.7 lbs)
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Basically the Invidia exhaust is a tank. Not sure I would have bought it if these weights had been publicized before. +15lbs for a catback is pretty hard to swallow. At least the weight increase is low and in the back. Even with the weight I took off with the headers and downpipe its still +3.5lbs overall, but the weight distribution is better.