can you remove the main cat and leave in the second cat without a remap?
and will it run without problems

 

From the advice I've read on here, if you decat the downpipe you should also decat the up pipe.

Yes, you should have it remapped.

 

STI's don't have cats in the up-pipe.

If you decat the downpipe watch out for boost spikes !

Either get a dawes device to reign in the boost, or get it remapped

 

is a dawes device sufficent to do the job, would there be much benefit in leaving the main cat and removing the second cat? ive fully decatted my other classic scoobs with no problems (both my95) but this is a 02 sti and i dont want to risk buggerin things up
thanks for the advice

 

Can only speak with experience of a MY02 WRX (not STi). As already stated, I believe the STi doesn't have a Cat in the 'up-pipe' - unlike the WRX, so this is not a problem.

If removing the Downpipe Cat on a WRX it will bring on the CEL if not remapped - I have experience of this, regardless of whether the second Cat is present or not. I can only presume that this would be the same for the STi - someone can confirm on here I'm sure. Therefore you would either need a full EcuTek remap or fit the CEL fix which is much cheaper. This would not cure potential boost spikes though if these were to occur.

What I'm not sure about is whether you can fit a Sports Cat without a remap? I ended up having a Sports Cat fitted but had a remap at the same time.

Removing the Second Cat should cause no problems, again my experience with the WRX has proven this and I can see no reason why the STi should be any different in this respect.