what good, would it do, if a replaced my standard one with an upgrade?

 

That largely depends on whether your current up-pipe has a catalytic convertor in it. If there is a cat in your up-pipe then there's a greater benefit to replacing it than if there is not.

You would find flow improvements by fitting a decatted up-pipe - just of different magnitudes.

 

oh right! so the up-pipe is if fact...a down-pipe? i thought they were different? why do people call them different names then?

 

I thought the up pipe was from the exhaust manifold branch up to the turbo !!!!

 

Up-pipe and down-pipe are two different things. The up-pipe runs from the exit of the exhaust manifold up to the turbo inlet. The downpipe runs from the turbo outlet down to the exhaust centre section. The original downpipe on all Imprezas has/had a cat in it. Some original up-pipes have/had cats (depending on model). All can be replaced with aftermarket alternatives.

 

aha! knew they were different! i have an my99 rb5? make a diff then?

 

In which case your car will have a cat in the original downpipe and will not have a cat in the up-pipe.

 

yup. so it's totally de-catted. so it won't make any difference? what year scoobs had cat's in the up-pipe?

 

No, I wouldn't say it would make no difference. Just less difference than if you were replacing a catted up-pipe (fitted on some MY01/MY02 cars). AFAIK the turbo-end of the original up-pipe is slightly constricted, so fitting an aftermarket pipe could improve flow.

By itself, I don't think you'd see a benefit greater than, say 5bhp. Poor value for money, unless done in combination with other mods.

 

Having said that, here's a cheap aftermarket pipe in the For Sale forum.