Changing the exhaust
 

I have decided it is time to make my 2003 WRX a bit louder – not the most original post I know. Right now it is completely standard other than a Prodrive back box but I want a little more of that burble in the cabin without needing to remap the car or replace the Prodrive back box as I like the look of it. I have been searching the forums for a while and realise that I have come down to 3 options. So, my questions are:

1. Will the Prodrive centre section (including the resonator) be louder than the standard WRX centre section and resonator? If so, enough to notice it?
   
2. Should I instead get a straight through centre section i.e. no resonator? Will I need to remap the car after this?
   
3. In addition to my decision on the centre section I could get the second cat removed using the Prodrive second decat pipe. I understand this will still pass an MOT but will I need to remap the car after this?

Cheers in advance for your advice, it’s much appreciated.
Ed

Just get a straight through centre section mate will make a huge difference the prodrive bbox makes a good noise and the centre section will help

My advice if you like the factory system but want it to be MOT friendly is:
1. Bin the WRX up pipe and replace with a Harvey up pipe to aid spool.
Not only does this strangle performance but the cat in the pipe also has the potential to break up and go through your turbo destroying it as it gets older and more fragile.
2. Replace your existing down pipe and centre section with a Prodrive sports cat and decat centre section, these can be had fairly cheap second hand.
Should be a little louder and make more power (but yes you'll need a map to take full advantage).

My old bug WRX made 281 on a TD04 with that setup after a map, but you'll definitely notice the difference.

Cheers for the advice, I think the centre section might be the way to go at the moment as it is so easy to do.

What I had heard was that the ecu is pretty conservative. If it notices anything out of the ordinary it doesn't try to maximise the power it gives you, instead it dials everything back in case there is a problem. So changing cats and remapping can give you great power gains but making changes and not remapping will result in power losses.

Having said that, in a month or so I may completely change my mind - remove a couple of cats and get a map done!

Exactly the 'conversation' I'm having with myself for my Classic.

Fitted a H&S back box on it but would like a little more burble so having looked at the options, I think a de resonated centre is the next step as doing the downpipe/de cat puts me into remap territory and I'm not wanting to go there just yet.

Yet ;)

On my V3 STi I have standard headers, full 3" system to include an Apexi sports cat and a Cobra de resonated mid section and back box with 3.5" tail pipe, sounds awesome! Other than this mod I only run an HKS panel filter. The car is run on Momentum 99 with octane booster and it runs spot on, no need for remap.

I've read and been told different things on whether or not a remap is required but I'm a safety first type when it comes to my car