i was on about the standard cat back exhaust mated to a 3" performance downpipe
....I've never quite understood the mix and match approach for an exhaust. It might cost a little more but I'd rather have the comfort of a stainless steel performance exhaust throughout and fully backed up by the manufacturer. You can't expect back up if you mix products - Milltek, for example, design their exhaust systems in their entiretity to accommodate back pressure etc etc.
Please correct me if I've misunderstood your post.
i think you have
. The exhaust has two parts. one is really restrictive to flow(the DP), one is really restrictive for sound(the cat back). you can change both and go for a free flowing better sounding exhaust but @ a cost of around £1000+, or you could do just the downpipe, release the back pressure, get a nicer burble and have £500 in your back burner to spend on other things.
Could you explain why miltek or any other exhaust manufacturer for that matter wouldn't offer any form of back up(which they do!!) if you were only to fit one half of the exhaust system. if this were true they wouldn't sell them like that at all, they would come as a whole TBE system. Also if your exhaust breaks whether full TBE, Cat back or downpipe, they are still covered by a warranty should they fail. So miltek under the consumer rights act would have to support/replace or repair anything that is down to their workmanship or product.
Also reference back pressure for the whole system. Myself along with many others on here, SCN and briskoda etc have all found the cat back gave naff all gains, so that would rubbish the back pressure claim ,IMO of course.