The cats are the main restriction in the exhaust system.

A cat back will make little to no difference to performance

Does anyone supply a de-cat that still has the "appearance" of a cat converter to get past MOT regs? 2006 HSE for Sale - £7,499 (Manchester)
http://www.rrsport.co.uk/forum/topic46383.html

Is it much of a job Mikey? I don't recall even looking under my Sport

darrenmcneill wrote:

Does anyone supply a de-cat that still has the "appearance" of a cat converter to get past MOT regs?

http://www.ebay.co.uk/itm/Land-Rover-stain...1381241865  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

What sort off job is it fitting a bigger intercooler and what are the performance gains

Not bad; naturally, the bumper has to come off but there's nothing particularly difficult about it. Mikey can give more details of the RS500 fit.

It brings with it the second largest performance gains after a remap. In combination with a remap, the effects are sort of multiplied. Hard to put a figure on it though, since the effect is not purely on the max HP figure.

Aside from that, they don't block up as much as the standard ones do and can be cleaned properly. I also like that it keeps the intake temps down generally.  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Am a layman
So what's the difference between a "cat back" and "de cat"

Thanks 2006 RRS Supercharged 4.2 HST muthuaflecka!

The catylitic converter is at the front of the exhaust system - a de-cat removes this, allowing a small increase in the low down performance, with the turbo spooling up more quickly. Cat-back is removal of the centre and/or rear silencers, which are after the cat - creating more noise, but little in terms of performance.  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Thanks lost for words. Will any decent garage be able to de cat? 2006 RRS Supercharged 4.2 HST muthuaflecka!

I would think most should be able to, but naturally, you'll need someone who can weld. I'm not really familiar with the 3.0 exhaust system, but on the 2.7, the manifold nuts have to be removed carefully, as there is a risk of snapping a turbo stud (turbo has to come out to replace it).  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver