Yes its a great mod for those without headers. Im Syd AU based and actually got this mod after speaking to the guy who got this done and seeing his pics.

When i got this done at the time i had an Xforce exhuast and K&N filter. Dyno numbers soley are useless as i know all dyno's are different but in my case i gained almost 13kw @ wheels. Then got it tuned and gained some more.

Ive since lost this mod as i got PPE headers but at a fraction of the price its a good mod to consider

Heres another of his pics (i didnt get any pics of my install at the time)

 

I'm sure the PPEs is at least a little better.

 

Absolutely. The sound alone is chalk and cheese and for the better.

It feels much more free flowing throughout the rev change, especially mid to top end but no dyno numbers to support this yet.

Ive since added a Takeda intake so when i get it retuned ill have to factor that but im confident the headers provided greater gains (well it feels that way anyway). Ps for the cost alone it would want to haha

 

This looks like a simple and effective way to make a bit more power. The ROI on this I think is greater than installing headers?

Anyone else speak from experience that has done this? Is the performance noticeable?
The only thing I don't like about it, is that you have to chop up your aftermarket or stock exhaust catback.

 

 

I was thinking guys with Silky or PPE Headers fitted that still need the cats for emmisions laws could have this done when re-fitting the cats, you wouldn't lose as much power re-fitting them with 3 inch exits.
Just what I would do if I were fitting headers.

 

Add cats to the midpipe, not the header.

 

There is a few of us Sydney ISF owners who have gone to the same dyno, same tuner. I can say that a few of them who have similar bolt ons to me and has since been tuned post headers (same headers, part of a group buy) have approx 20kw @ wheels more than i currently do.

When i get mine retuned in a month or so im expecting similar numbers to them as we'll have similar mods (I/H/E)

Even without the dyno numbers to confirm my car's performance, as soon as drove it away i could feel the difference without a doubt (to me anyway). Now, looking back, im happy with no regrets and im confident in the power gains but here in Syd, the cost of the cat mod vs PPE's and install is about 4-5 times the cost. So $/kw the cat mod is a better bang for your buck but if you have the $, its hard to wipe the smile off your face hearing and feeling how the headers changes the exhaust note and helps the car to breathe better

 

Yep thats it. When i got my PPE's installed, it wasnt a true bolt on due to me having this mod. Those who didnt have the cat mod, it was an easier install as it did bolt straight on so the installers had to do a bit of exhaust work to get mine to fit

 

Does widening the primary outlet cause any codes with the O2 sensors?

 

Yes to the midpipes