Fuel restriction on 200 hp Johnson.

[Afishionado]

Bought a used bay boat recently with a '97 Johnson Ocean Runner. Engine runs fine but the check engine light comes on at WOT. Light goes off after I bring the throttle back to cruise RPMs. Read in my engine manual that is a fuel restriction causing the vacuum sensor to go off. Changed the fuel/water separator filter, checked the fuel filter on the engine (clean), and checked the screen on the pick-up tube and the anti-siphon valve operation. Found no problems, so took it to a shop to draw a vacuum on the lines to find out how much restriction I had and where. Well the anti-siphon has a little over 2 inches of vacuum and the fuel/water separator has about the same. My fuel flow meter draws a little but nothing to be concerned with. Overall, the whole fuel line with bulb is drawing about 5.5 and setting off the sensor. He says he's going to try a new brass anti-siphon valve to see if it helps, but if it doesn't, I have to remove one or the other. Either the anti-siphon or the fuel/water separator. I don't want to remove either one, you have any other suggestions? Thanks for any help.