Milltek, quite rightly in my opinion, won't launch a product until they are satisfied it will work well. Producing performance exhaust systems for cars involves much more than just bending tubes.
Sure, I agree 110% on it not being just beding tubes. Only, they do not bench-test cars with their exhaust, so they do not really know if it works well, if you know what I mean.
Oh, you are so, so WRONG with that statement. Milltek certainly do test their exhausts. They repeatedly run them on a rolling road dyno, and constantly tweak the spec, not only for "performance", but also for clearance, and general fit and finish.
Milltek are extremely highly regarded, thoughout the entire aftermarket and tuning sectors of the motor industry, be that Volkswagen or Vauxhall, that their products are consistently the best finished, in terms of quality, fit, sound, and performance. Milltek have built up such an enviable reputation, you can be assured that they are a fit first time, and forget product. (Unlike something else listed in this thread title 
)
I do not think I am wrong, TT.
THis is from their webpage:
If you’ve a new model of car and want an after-market exhaust,
then Milltek Sport may be your only choice: it’s quick to develop
them for the latest models. But even if you don’t have a new car
there are plenty of good reasons to choose the UK brand.
The company started as six enthusiasts making stainless
exhausts for classic cars in the south-west of England. Now the
team has grown to 45 operating from two sites in the Midlands.
Aircraft-grade 304 stainless steel discolours less than many
types because it’s anti-magnetic. All Milltek systems are made
entirely from this material, including the internals and clamps.
When pipework needs to be shaped it’s done with mandrel
bends – these mean it’s not crushed so it retains the same cross
section throughout the curve, which gives the best gas flow. The
exhausts have a bigger bore than original, and increase both peak
performance and mid-range torque.
MD Phil Millington is keen to stress this: ‘Take the BMW 335i
fitted with our system. The peak power is increased by only
21bhp, but the improvement in mid-range torque means it’s a real
rocket. The systems we make for road cars are designed to be
just that. They give real-world improvements in the cars. They
feel quicker and drive better than standard.’ He’s keen to mention
the firm’s reputation for excellent customer service, too.
Their exhausts are quality products – as good as original,
claims Milltek – and that means they’re easier to fit than many
competitors. A full system for a Porsche 911 GT3 will set you
back a not insignificant £3995, but that includes manifolds.
Milltek Sport’s range doesn’t include cat bypass pipes.
Although these are cheaper, and will give better performance
than high-flow sports catalytic converters, the firm doesn’t
include them because cars without cats aren’t generally good for
the environment. They’re often illegal, too.
Everything is designed and made at their factory in Ilkeston,
Derbyshire.
Significantly, the firm doesn’t use a dyno when
developing its exhausts. It has the knowledge and experience to
build good systems without it. Plus, as they’re often designing
systems for the latest cars it’s often the case that engine
mapping specialists haven’t managed to ‘crack’ the ECUs yet, so
the cars can’t be remapped. Milltek Sport knows that most
owners getting an exhaust will get their car remapped, too, and is
confident their products will work extremely well when they do.
