High Pressure Leak! Help

[sweeda]

I noticed that my #5 fuel line (rail to head) was wet. saw that #6 had known problems so I replaced it. cleaned area checked the next week (about 700 miles) and it was wet again. ordered and replaced #5 fuel tube. Now truck seems to run better. 2weeks later checked it agian and dang it! it's wet agian. I just installed a rail pressure gauge & is 5-6000 psi ok at idol. running down the road at 60 to 65 mph its about 15-16000 psi does this sound right. and does anyone have a idea how to find this type leak. at idol there is no sign of fuel leaking and i'm not leaving fuel on the ground.