That is what I tried to explain. (not always as easy in another language).

The powergain comes from the pre cat delete and bigger downpipe. I dont think you will loose

much (if at all) when you go back to the original (OE) exhaust system, at least the cat back part.

And mostly those systems are sold for near nothing, so an easy and cheap way to get the car quieter.

was typing as you replied, thing is I'd kinda like some xtra noise at WOT, just not so much noise when driving around normally on a light throttle.

But will a standard system (from the pipework section back) not reduce the power or torque at all?

But will a standard system (from the pipework section back) not reduce the power or torque at all?

That was my thinking especially with K04. K03 is fine with standard cat back, My k03 gave 280bhp on a dyno dynamic RR with standard cat back.

To be honest, I dont know from own experience, because I didnt have a TFSI myself.

All I know is that the power gains come from the downpipe. That was stated in the German forum and in

a couple of Golf V forums.

But it still is the cheapest way to get the car less noisy. And if it doesnt work, you can still get the Jetex system.

If you look at the modern engines and how they react on other exhaust systems, you will see that an aftermarket (sports) exhaust system

will not give you much extra power. Often even less than original.

But your car is modified and therefor might react differently on the different systems.

I've got various rolling road printouts from JKM in Portsmouth (who I believe have an accurate Dyno) showing a fairly consistent 325BHP, and one at 328Bhp, I just can't beleive that putting a standard factory exhuast system back on won't strangle this somewhat ?

Am I being really stupid here?

I'd probably not put an OE system back on as I think it'll subdue the noise too much and it must weight a fair bit more than a SS aftermarket item.

Also, I'll probably stick the Piper system on Ebay to recoup some of the cost, even if this only gets me £150 back - think they're about £400 new? (There's always going to be someone who wants to replace a standard system with a modified one, but doesn't want to spend loads.)

The thing is the pipewerx DP will come with a reduction connecting pipe to take it down to stock cat back, I'm not sure what Dave did about this.

That is correct - the Pipewerx is 3" all the way through to the end where it reduces to 2.5". This is part of the pipe rather than a separate reducing piece if that makes sense. The Piper cat-back is 2.5" so they just slot together. If a different sized cat-back is used, the 2.5" part of the Pipewerx will need to be chopped off and a joining pipe used. Hope that makes sense.

My feeling is that a standard cat-back will inhibit the flow to some extent on a K04 but not much - it may knock a few horses off but if you can get a hold of one cheaply it is worth a shot to see what happens with a before and after dyno run. It will be a simple fit on to the Pipwerx DP. Alternatively, BCS to a version of their cat-back with an extra silencer to keep things quiet but it is a 3" pipe so should not have much restriction at all.

So you could either chop your existing DP reducer off or keep the reducer on and join. The Jetex cat back comes with a reducing kit to take it down to stock DP so should be fine if you chose that route. If you want 3" all the way measure up and get a pipe to replace the DP reducer.

Another thing to bare in mind is the stock (and I presume pipewerx) DP has a bend in the pipe to centralize it, I had to chop that bit off to fit the connecting pipe. It will take a bit of lining up but is possible.

cant you just buy the resonated pipe for your current cat back?having 2 silencers in the system will lower the noise levels