15* and 17* hpop differences?

[melmount]

Whats the difference in the 2 hpop's? I know pressure but anyone know how much? i have been chasing injector noises. I have done multiple threads. I am getting it narrowed down. I bought this truck it would and it would not start the next day. It turns out the hpop gasket was for a 95 obs truck. Thy are different then the 01 etc pump gaskets. It bled down over nite. I have that fixed but still cant get the motor right,. I have cackle real bad. I can unplug injector 8 and no change. I can unplug 6 no change. If i unplug both its quiet. Its either a fuel problem or hpop pressure problem. I can unplug alkl injectors one at a time and no ticking goes away. It does not do it cold. Makes me think oil. Since the pump had the wrong gasket its a good assumptyion that someone put in a reman pump(reman sticker on it) but its the oldr smaller style. What would this do? I have 3275 kpa's of pressure at idle. Thats about 475 psi.
thx