Makes no real difference pre-or-post remap - I'd say pre myself as then you can get a custom remap done specific to your engine, but then I did it the other way round, so what do i know?!!
My insurers didn't care about the DPs - it's not a visible part of the car so it won't increase it's 'value' to thieves. And the insurance company won't understand that it increases performance.... my insurance company (Direct Line) lumped all the mods (bar the remap) together and charged an extra £50.
DPs will only better the
engine, in that it will reduce the back pressure on the turbos so that they spin more freely. However, it does also mean that you will lose one set of catalysts, so the secondary cats in the middle of the main exhaust will be doing more work, and will deteriorate marginally quicker.
Catless DPs to change the sound - it makes the turbo spool a little more noticeable, and gives a throatier sound to the engine under revs. Not very loud though - you won't get people turning heads thinking wondering what's going on...
With catless DPs you will also need to do one of the following - a) either relocate the rear lambda probe sensors to
behind the secondary catalysts; or b) install 02 simulators in the ECU box.
SerJames and I strongly suggest you follow the first option - relocate the sensors. The reason is that then you don't need to mess about rewiring the ECU. Also, the resistance modification of the O2 simulators is not exactly correct for the UK market - works fine in the US, but we sometimes get limp codes here because the voltage change is 'out of bounds'.
You essentially have two options for downpipes - RissRacing and AR Design. I personally think you should stay away from the RissRacing pipes - when being installed on SerJames' car, we discovered they didn't fit properly first time in and also aren't really engineered for right hand drive cars (our steering rack placement is different to the left-hand-drive cars and there's a chance it will foul against the top lambda probe location). These problems may have been eradicated now since they were installed on SerJames' car - Evolve might be able to shed more light on this, but from speaking to RissRacing distributors in the States, it seems that there are still 'communication' and fitment issues that still need addressing
(This is NO reflection on Evolve - this is an issue that lies solely at the feet of RissRacing)
The alternative is that you go for AR Design, where like RissRacing you also have the option of buying high-flow catted downpipes (and engineered specifically for right-hand-drive specific configuration). The advantage of this is that there's no need to relocate lambda probe sensors, as you're not eliminating the front cats. Also, being high-flow versions you get most of the power gain of catless DPs, without any of the hassles! I brought a set of catless AR Design pipes into the UK for my car, and had them fitted at Birds (who also installed the RissRacing pipes on SerJames' car and hence discovered a few 'issues'). Birds were so impressed that they ordered a high-flow catted version for their own demonstrator, and as a result are now importing AR Design products (downpipes and oil cooler) into the UK. I'll be doing a review of the AR pipes in due course - keep an eye out... For Birds, contact
www.birdsauto.com - or call and ask for Kevin Bird.