downpipe and more...

ok i was reading the last issue of power pages, and in it they text a 92 eclipse turbo. stock it was like 183 hp, after a downpipe it was 219, then a fuel cut defencer put it at 267, then a fuel pump put it 290. total it cost only 640 bucks. but then in a evo they put in a downpipe and it dropped them about 5 horsepower, im confused about this, for example what would a new downpipe do to an integra

downpipes are for turbo cars...


most integras don't have factory turbos, therefore adding a downpipe to a turboed one isn't gonna do much cuz its already got an aftermarket downpipe.