Currently in my 2005 blob wrx I have a 2.75" bore milltek cat back and a scorpion second decat replacement pipe, I'm considering either a decat downpipe or a decat uppipe now, but which one is best to do?

If possible I'd still like it to sail through an mot and display no warning lights on the dash

what's the best option, pros and cons of each?
Thoughts?

Cheers Jeff

 

Up pipe is safest as they have been known to break up and send bits of themselves through the turbo, which is somewhat less than ideal... plus you can just get an up pipe from a breaker from a Classic, newage STi or 2.5 WRX if you want to save a few bob as none of those have a cat in the up-pipe.

 

I have a decat downpipe on my newage sti. I previously had a cat back system but recently upgraded downpipe to make it a complete catless system. I've got to admit not sure why i didnt do it before, the difference is amazing, car breathes alot better, no lag, better bhp and torque to say the least.

The only other way would be for you to get a sports cat

 

btw i've got a used downpipe for sale which i bought thinking it would fit my 04 newage sti but it didnt. Its shorter therefore would not fit but i think it may fit the earlier models if yours is a 05 hawkeye.

Contact me if interested.

 

You'll see the biggest benefit from a downpipe. Earlier spooling too which is nice. A good remap afterwards of course

 

Hawkeye is mid-2006 onward.

IIRC, all newage Impreza WRX / STis (hawkeyes included) share the same system aside from whether or not they have a cat in the up-pipe so I suspect it wouldn't fit the OP's car either.

If you want to pass the MOT, you'll need at least one cat in the system (downpipe is usually best for emissions). As mentioned above, a sports cat will allow for better flow (if you're lucky, you may be able to pick one up from a PPP STi) as an alternative to a full decat.

Mind you, if you're fitting a decat/sports-cat downpipe, there's not much point having the one in the up pipe either really.