The best replacement for downpipe is cat back.

The best alternatives to downpipe are rated as following:
★★★★★  cat back
★★★★  test pipe
★★★  turbo back
★★★  headers
★★★  header
★★  uppipe
★★  full exhaust
★★  straight pipe
★  bellmouth
★  front pipe
★  intake
★  perrin downpipe
★  catted downpipe
★  dump pipe
★  wrx downpipe
★  downpipe
  cobb downpipe
  cobb
  midpipe
  up pipe
  catless downpipe

Your alternative for downpipe is not listed? Suggest!
Speaking about downpipe, one probably shouldn't forget about stock exhaust wrx.

Other search terms related to downpipe and their ratings are:
★★★★★ stock exhaust wrx
★★★★ turbo
★★★ exhaust
★ stock exhaust
★ spt exhaust
You have in mind a companion for downpipe and it is not yet here? Propose!



Google Trends

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downpipe
cat back
test pipe