also try and look real close when things are running, is it possible that one of your delivery valves is seeping and whicking/dripping and tricking you into thinking the lines aren't mated and tight?
I've used teflon tape to seal where the hardlines fit into the injectors. ya'll can hate if you like but it works for a pretty long time.1 only just started to leak again and it was because i took the lines off twice without replacing the tape. IMHO it works pretty damn well. Don't need a ton. It fills the valleys in the threads and has so where to go when the diesel is pushing on it. Doesn't seem to disolve either.