Seacow, the fire then die you're experiencing is definitely an air intrusion issue. However, the caps and o-rings ain't all that sensitive as everyone is making them out to be - ALL my hoses are cut a bit too long and kinda weave between the injector caps and I have no leaks whatsoever. Also I once had to remove the line off the #7 injector while in a truck stop so I can tighten the injector down in the head, during this I apparently cocked the cap and when I fired up the truck it was dripping fuel - I simply wiggled the cap a bit and the o-ring seated again and it's soon to be an year since then with no issues whatsoever. I'm using a GP Sorensen kit that the PO had left for me under the seat of the truck when I got it...
Also, I will have to disagree with what Jim says - I sometimes have to fire up my truck on low idle so I don't wake up the neighborhood, she starts up just fine in cold and stays running - granted she rattles a lot and for the first minute slightly misfires, but she stays running and I can drive her immediately. So the solenoids ain't your issue, and neither are your GPs.
I'd suggest that you look into the main return line from the engine back down to the frame rail, that started leaking on me last fall it it took me like a week to figure it out - after replacing the rubber hose there I also removed the return hose from the filter head, I have since then had the heater o-ring develop a leak but since it is at the highest point of the filter head and there's no return line there no more it couldn't drain my filter, and I was starting just fine, only making a mess while running.
On the olive donut behind the #8 injector - not all trucks have that, mine for instance don't - you will only have it if you have a large steel return line coming off your IP and running on the driver side of the intake under all the injector pressure lines. Trucks with that setup also have a cap on the #2 injector with only one port, and there's just one return hose hooked up to it, leading to the #4 injector. For comparison my truck has no IP steel return line, instead the IP return flow passes through the #2 injector cap (the cap has two ports at 90 degrees from each other), and then passes through all the driver-side injectors till it reaches the rear of the engine. I suspect this is why I have the 1/4" return lines, an not the 3/16" that is typical for the '6.9 trucks that also have the steel IP line - the injector return lines in my case have to handle the flow from both the IP and the injectors themselves. This is actually a factory setup, I haven't modified it at all, other than when I removed the return line from the filter head I ran its hose from the # injector to the IP return port (with a Tee fitting) so now the IP split its return flow through both banks of injectors - they still Tee together in the rear of the engine and from there down it's one main rubber line (the one that was leaking on me last fall).