My impression is that if the tube isnt suffieciently filled with an inert gas ( purged??) the weld will be brittle. Seems to be a chinese thing as all the clone stainless manifolds suffer joint breakage dont they.
It's a failure, it's not chinese. I'm having a headache with an el-cheapo clone product on my work now, and guess what, it's made in the UK!
Btw, it's not necessarly gas, quick google says that Milltek MIG welds the outside, and TIG the inside.
source:
http://pumaspeed.co.uk/showdetails.php?id=785
There can be a lot of reasons for the crack, lets not question milltek's quality so hastly.
Problems with the raw material beyond manufacturer's control?
Maybe wesley hit a puddle and cooled the joint when he was driving the car on a rage?
Bad installation/support of the exhaust system?
The list of possible reasons (or any combination of) is endless.
Fwiw, I sell valves to oil and gas companies for a living. They'd pay good money to make sure
everything is designed/manufactured to standards and tested for possible faults. (heat treatment after welding, hardness check, pressure testing, low temp testing, inspector for everything, a 2nd inspector to make sure, and a whole lot more), and even after passing all that, failures still occur, though rare.
Milltek makes how many thousands of kits each year? and how much do they profit from each kit? If they were to do FEA on each and every of their product, use a high safety factor for all considerations, and test the product to make sure it can survive the pressure, temp, and loadings in the worst possbile case, none of us could afford the damm exhaust.
No disrespect to milltek or any other exhaust manufacturer, but I was told that most "research" is actually involved in test fitting the thing, and if it can be driven around fine in a car for a while, you have a new product! Maybe some companies would go to the extent of testing with a few different pipe ID, layout, or things like that, but nothing one would call a full blown research/analysis. I'd be glad to be proven wrong on this one.
Personally, I'm surprised that so many kits survive for years. Still, I'd gladly buy a milltek and ask for a discount. Just wont expect it to last very long though. That said, I wouldnt be too happy in wesley's position too.
Just for comparison, this is what a properly engineered exhaust should resemble, and i believe only huge factory backed companies have the money to make it happen. Remember, this exhaust is also supplied to the public, and not a one-off race part, so it has to last fairly long as well, especially when it cost a cool 20k usd.
http://www.bespokeventures.com/blog/2009/01/24/the-definition-of-quality-for-2009/
*btw, I'm not affiliated wiht milltek or any exhaust company. sorry for the long rant, I love quality stuff that are designed by a big bunch of nerdy virgin engineers. It's just that Milltek is a business with a specific target market (i.e. common drivers who couldnt care about the last 0.5hp or few extra grams), and found a comfortable spot for quality vs price. Srsly, who here would want to pay such money for an exhaust?
My Mrs tells me it's not what you got, it's what she has in the bedside draw.......... 
LMAO
