I have a 1994 WRX with TD05 and Z4 ECU and it is fully decatted (the car only had the downpipe cat as standard).

I am getting slight transitional and lift-off DET issues, which I belive is due to the increased fuel requirements of the full-decat.

I am thinking about putting the downpipe cat back on. Do you think it would be better to put a centre cat from a UK car on instead? I thought this might give me better response than the downpipe cat but also solve my problems.
Obviously this requires the additional expense of buying the cat so I will only do this if the difference will be significant.

Or should I remain decatted and get a new uprated fuel pump, and hope this, along with cooler weather is the cure.

Long term goal is to get it Mapped properly but this has to wait a few months, so I need a good reliable fix for now that give me the best drive.

 

I've got just a de-catted downpipe, with standard exhaust throughout the rest of the system and I've had to have a re-map to solve DET.

So prob best to re-cat the down-pipe... may save a job later on...

(2003 STI)