Which parts do i replace on the exhaust for max performance?
 

I have a 2000 W Reg UK Turbo impreza and i cant get my head around all the different exhaust parts. i keep hearing of:

- up pipe
- down pipe
- centre
- backbox
- 2 cats?
- manifold
- header

I want to get the best performance i can out of the exhaust. will probably be taking it to hayward and scott as my mate had his done there and was really impressed.

I dont want to fully decat it as i have heard this wont pass an emitions test. so can i remove 1 cat and replace the other with a sports cat?

does an impreza have an exhaust manifold or are the called headers? have tried to pm harvey about his ported ones but no reponse yet. are they good or shall i have new ones made?

All help greatly appreciated

Cheers Tom

IMHO:
'Headers' is a term used on here for replacement exhaust manifold made usually from thin wall stainless steel tube. Unless you have a well modified engine forget them.
I feel you will be best off with ported stock exhaust manifold and the stock up pipe (which feed the turbo).

Harvey is an ace at doing these but David at Welcome to the API website does them too.

Change the down pipe to a sport cat and the rest of the system with a matching centre and back box. H&S make a nice system, the Revolution system is good too and quiet.
With a stock engne a 2.5'' diameter system will work well.

That will open the exhaust side of the engine; fit an STi panel filter to the stock air filter housing or a Green Panel filter.

Graham.