Mine failed do to user error. I replaced the Orings and crush washers under the delivery valve holders, and when I went to torque everything down to 25 FT/LB, I had never used that low of a torque setting with a click type torque wrench, I snapped every single one, and even broke one off into the pump.
I ended up using an easy out to remove the threads broken off out of cyl 5 gallery. After that I put everything back together with new delivery valve holders and washers and the car ran. But then when I revved it a bit it took off, but I was able to shut it down before any damage.
I had tons of fuel in my sump now. I drained the oil and put in fresh oil then started it up. Now it idled like crap but it never took off again. So I drove it around thinking I had washed the cylinder walls and unseated the rings. It drove fine, but just idled like crap. So I took it all apart again..

I then removed all of the delivery valves, got a magnet and began pulling the barrels out to see if they were misaligned with the pins. I got all of them out but #5, the one I broke the thread off into. It eventually came loose, but could not lift more than a half inch out of the fuel gallery below the threads. I tried everything, even putting a coat hanger into the fuel spillover hole in the side of the barrel to lift it but It wont come all the way out. So I PB blast everything put it all back together with new washers again and started it up. It ran Well and warmed up. I then gave it a tiny rev and it took off again, and I shut it off before it could do damage. I checked the dipstick and it was over filled with diesel again. So I drained it and put more in and started it up. It idled like crap again.
SOOO I need to pull the pump out. Either when torquing it down I cracked the housing and the barrel sits lower now advancing fuel, or there is an aluminum piece of threading jammed against the side of the barrel in the fuel gallery causing the barrel to torque unevenly...

Either way my fault not Bosch.