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For a while I have been having trouble with the lower charge pipe on my car popping off under hard driving. The pipe would stay on and hold boost, but unless the hose was very carefully installed and degreased, it could work itself loose over time. Silicone is a popular material for hose, but it is very permeable to oil, which just made the problem worse. I believe part of the problem is with the CSF radiator which pushes everything back and results ina few key parts not fitting correctly.
A few solutions existed, one of the problems was that the 45 degree bend on the turbosmart hose I was using is a bit different from the stock rubber piece, which is probably closer to 60 degrees. I had a hard time finding a suitable hose, and would still require the hose to be cut to the right size. I have never been able to cut silicone cleanly, and I also noticed the lower charge pipe itself was rubbing on the fan. So I decided a custom lower charge pipe was probably the best solution which covered all the problems.
Probably the best material to make the pipe from would be aluminium, but with not much experience or confidence welding aluminium with my TIG welder, I opted with the stainless route. Stainless sanitary tubing is plentiful from Aliexpress and ebay, and you can even buy barbed tubing which is perfect for the charge pipe joins to silicone hoses.
One thing to watch out for with stainless is the chromium in stainless steel. Without argon gas shielding, the chromium is quite reactive and will oxidize and crystalize when when heated during welding, resulting in "sugaring" which will be lumps of crap that form which would form inside of the tubing welded. For a charge pipe this is probably not a big deal, but in this case I opted to back purge the pipe, filling it with argon so the back of the weld is shielded from oxygen.
The charge pipe was made from a bunch of 45 degree bends and a small bit of straight tubing. The pipe was welded without filler and just fusion welded with the TIG torch. Was happy with how it come out, a few spots that didn't come out perfect but got some decent experience and definitely improved towards the end.
The charge pipe now fits perfectly with lots of clearance to all the surrounding parts. I was able to use a short 2.5" silicone joiner that can be bought off the shelf should it need replacing (after a while the oily instake charge air oil permeates through and is just easier to replace). The silicone joiner now is not under tension on installation and is lined up squarely on the pipe beads, so should be a nice leak free setup.
Upon first test drive, the car already feels less jerky and responsive, given that there is no longer a slight boost leak.
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