Yamaha Power Loss

[Rf90]

My 2006 f90 yamaha just loss power (from 4500 rpms to 1500 rpms). Don't know which part to replace. High pressure fuel pump, just the filter, or both. I've already replaced the obvious parts like spark plugs and inline fuel filters. My computer pulled up a code 37 which is something to do with the idle speed control (ISC) valve. When I run the fully open ISC valve test it kills the motor, but one mechanic I talked to said to start with the high pressure fuel pump. Both these parts are to expensive to be guessing at and replacing for know reason. Any ideas??????????????????

[boats.net]

Need to run fuel pressure and fuel vacumn test at the point it looses power to see if have a fuel restriction or a fuel pump problem.