Hello Markus,
As Mr Dragonslayer states about the ebay accordion manifolds, I concur with his assessment that they are bombproof. The flanges are in mild steel but they are thick, the main body is in 316 stainless or later production in 904 stainless, I was in contact with one of the manufacturers in China years ago. They are so cheap because they are robotically welded. Once the factory is set up for welding there is no variance and the welds are perfect. I have had one on my 94XJ for about 20kmiles and thence I had a complete stainless system built onto the car including the cat, right back to the tailpipe. The 904 variant can develop a powdery surface rust, but this is just the stainless forming a protective skin of oxidisation.
I have also seen OEM manifolds repair welded and there is nothing wrong with that. I was told the engine mounts must be in good condition, as its that rocking and the inflexibility of the OEM manifolds that cause them to crack.
I am not a great welder so to have someone repair it was more than half the cost of a new stainless flexy and you should get new gaskets included top and bottom.
Keep up the good work of keeping these iconic cars going for as long as possible.
Best regards. G.
