^agreed, I think there is something wrong with your IM manifold seals, they should be much firmer than the a-ring at the top. did you have the black plastic spacer installed that goes between the fuel rail, return line and mounting tab on the intake manifold?

 

I'm glad you agree with me but i'm 99% sure he had the spacers in. If he hadn't his fuel rail would snap before he felt any torque on the fuel rail bolts. This is one of the things the spacer does. Not only for placement of rail but also keeps the fuel rail from putting too much pressure on the injectors at which point **** would break.