Morning all.

I purchased a TSL Firestorm back box last week and it sounds fantastic. I have noticed that the car pulls a little better especially at higher revs where I used to feel the power dropping off hard past 6,000 rpm.

I have an MY03 STi by the way.

Noise aside as I don't care how loud it gets which would be the best option to free more power?

Do I replace the centre section first or leave the stock centre section and remove the 2nd CAT?

I know the downpipe is the most restrictive but I want to replace that with a Sports CAT when I can afford it.

 

I've replaced my d-pipe with an H & S decatted jobbie
replaced the B-Box with the PPP prodrive unit
and left the standard centre section in situ.

Initially I had overboost problems, surging problems and then CEL issues (2 boxes in all).

Finally took it to Powerstation and had the ECU mapped

Problem solved, car is fantastic.

Powerstation did recomend de-catting the centre section, but that would mean MOT failures (and having to keep the old exhaust in the garage)

 

I want to leave the downpipe as stock for the moment.

Can anyone tell me which will give better performance gains between a straight through centre section or decat the 2nd cat??

 

I'm no certainly no expert so I can only tell you from my own experience. I've a MY01 WRX, but as far as I know the exhaust is basically the same on all newage. From the turbo back, there are 4 sections, Downpipe, cat pipe, resonator & back box. Forgeting the downpipe & backbox, the next best thing to change is the cat pipe (or 2nd cat) as this is more restrictive than the resonator. I've done the same on my scoob leaving the original resonator pipe in place to keep the noise down but adding a Ninja backbox and the improvement is very noticable. The pickup is better low down the revs and the car seems to pull harder and longer. I've also got an STi panel filter and these few mods alone have really put the back on my face.

Hope this helps.

BTW I got a 2nd hand cat pipe from Scoobyclinc for only £40 plus fitting.

 

That's what I was looking for mate

I'll start by removing the 2nd cat and see how the noise/performance goes.

 

im in the same position and was worried about overboosting/spiking? by removing the center cat.......still unsure really, i want to keep ine as stealthy as possible :P

 

I don't think overboosting becomes a problem until you remove the downpipe cat as this is the most restrictive part of the exhaust system.