I installed a fuel pressure gauge in preparation for shimming the fuel pressure regulator. One thing I noticed immediately was that within 5-10 seconds after the ignition switch being turned off, the fuel pressure had dropped to zero. Is this normal or leak injector or some thing to do with fuel pump?

 

That sounds normal, it's a return system, so once the pump stops running pressure will eventually drop to zero.

 

So in order to avoid this when setting up your pressure you will need to keep the ignition on and jump the fuel pump through the diagnostic FP in front driver side of engine bay.... little black covered box. This will keep the fuel pump at max.

 

I think this also has to do with the design of the FPR. I think the stock FPR holds pressure moreso than some aftermarket units. I think it could also be the fuel pump itself.

I would also double check that the connection from the fuel pump outlet to the hardline is 100%, many threads on this. If that has a leak there it would depressurize the system quickly once the pump stops and you'll also have less fuel pressure under load.

Dale