Sounds like no one has been able to pin down the actual problem. I have the same starting problem with my 2001 C70. It's been back to the dealership many times and each time they can't figure out the problem. There are no codes to give them a clue (Gee, how did they fix cars before computers?). It has only happened for them once so they know I'm not crazy.
What I have been doing which has been successful 9 out of 10 times is: when the car won't start I leave the key turned but don't crank the engine for a few seconds. I'm figuring it's a fuel pressure problem so I let the pump run for a few seconds and the crank it over and it starts almost always. The fact that this is not 100% successful makes me think it may something other than or in addition to fuel pressure. I have suggested the dealership replace the fuel pump but they don't want to do it unless I pay for it, so naturally that has been done yet.
I am curious about the dry gas. What is it and where does one get some?