Yamaha F115 loses RPMs when WOT

[1st70LT1]

I have a 2004 Yamaha 115 4 stroke F115TLRC. It idles great in the water and on the hose. Press the button in on the shifter and rev the throttle, the RPMs jumps up to 6K for a second. Changed the water/fuel separator filter, fuel filter, all the fuel lines, new spark plugs, etc... When I have the boat in the water and throttle up to take off, it planes out slowly. As I increase the throttle up to 38-3900 RPMs it is okay. But when I give it more throttle it acts like it starves for fuel and the RPMs start to drop and I start losing speed. Anyone experience this with their F115 outboard? Checked the gas in the fuel filter looked clean. The fuel in the water separator was clear. I pulled the intake manifold unit off, disassemble the VST tank, checked the filter on the bottom of the pump motor, some debree, but nothing that would restrick the fuel flow. Pulled spark plugs to see if any were gas fouled. All were dry which indicates none of the injectors are not leaking. Checked the inline filter that goes from the fuel pump assy to the VST tank, clear. Made sure all fuel lines are clear. Checked the pickup in the fuel tank, not clogged. I've changed all the other filters. No difference in motor performance. Now looking at some of the parts diagrams on line I notice a couple of other parts that I think maybe causing a problem. After pulling up some parts websites I notice there is a Pressure regulator. It is under the FUEL INJECTION NOZZLE category item # 9. Then looking under the FUEL 1 category #14, fuel pump assy, there are two diaphrams. And then under the INTAKE 2 category, #13 is a filter assy that mounts under the fuel control valve assy. Could someone tell me if they have experience any problems with these items? I am running out of thoughts as to what is causing this problem. I do want to mention that when I first put it in the water after sitting over night the trottle response is good but as I run it for a few minutes and then try to trottle up it acts as if it starves for fuel. If you have any questions to help determine what the cause of the problem may be please ask. Another thought that I have, if the vent line for the fuel tank is clogged would that cause a fuel restriction? I would appreciate any help.
Thanks

[herb.wilson@uno.edu]

Had a similar issue with a 2006 f115. Replaced the racor fuel water separator, vst filter, all the fuel filters (including the one between the low pressure fuel pump and the high pressure fuel pump), and checked for an anti-siphon valve in fuel tank. I also sent the injectors off for cleaning (sonic cleaning, new internal screens and o-rings). One, all or some of those things did the trick. No bogging problems since. Maybe low pressure fuel pumop cannot keep up. Maybe try testing it.

Also try an external fuel tank with new fuel line all the way to the engine if possible.