i believe the only stainless on the 42DD is the cat the pipes are cheap aluminized mild steel, short lived coatings are xtra $$, their pipe are way $$$$ for materials used IMO!!! i am looking to get a cat delete setup for offroad, seen them on UK forums but not in the USA, stainless OF COURSE!!

 

if this is off road use which is different for a TT normally get a cheap one as when I think off road think BAJA off road as that will pound the crap out of the bottom of a TT... am on the UK forums all the time for years you might be surprised they can ship from over there pretty cheap check it out might work for you..

as for 42DD still have to recommend them highly on their 225 down pipe still have found nothing better in quality and power gains..... and yes wish it was le$$ ......

 

OK, I took a chance and bought the China piece. Seems to be put together very well. Clean welds. My shop test fitted and they do not see any issues. The only thing I'm doing to it is cut off the 2.5" section off the end and adding another bung for an O2 meter.
Per the sellers site they use 321 stainless, not 304. From what I've read up on it 321 is much superior for turbo applications with the increased heat.

A few more pics following. Enjoy.

 

The other pics.

Oh, I'll add that the 42DD downpipe I took off didn't look bad off the turbo and down to the turn-back, but after that the salt had eaten it up some. The outer flex braid was worn off in places and the collar on the front edge of the flex section was half gone. I probably could have reused but I'm glad I took a chance on this, especially at the price.

 

look up burns stainless they tell all, says 321 is a better stainless for higher heat still good on rust, as stated i had coated headers, little difference only in your wallet. IMO 42DD tries to convince the buyer to buy his inferior material product at only a slightly lower price, i never used grade 409, but the OE does now, IMO they should at least use the 409 grade for their $$$, it gets ugly but not supposed to rust thru, removal can be tough, my 10 yr old 304 stainless pipes in pa 190,000 miles a work car driving thru snow and rain, not a spec of rust, in the long run STAINLESS is CHEAPER!!!!