2003 yamaha 90 4 stroke hesitation at mid throttle

[Skinny1]

Hello
Have a 2003 90hp 4 stroke. Have had the carbs cleaned and synchronized. Still have a hesitation/ stumble between 2000 and 3000 RPM. Starts and idles great. Gas is new, 91 octane. primer bulb stays firm- no air leaks in hose. above 3000RPM it takes off full power. Im wondering if the thermal choke valves could be doing something to it? Not sure how to proceed to figure it out. Any help appreciated.

 

[William01]

Spark plugs?

 

[Skinny1]

i cant figure out how to make a picture smaller on iphone. they all look similar to me. will get another set and install.

 

[Skinny1]

Actually, number one plug is lighter color than the rest.

 

[Skinny1]

Number one is a little lighter

 

[Skinny1]

I assume either a port is dirty yet or an oring is leaking on cylinder one? Since it starts and idles excellent, which ports or Oring, or gasket should i look at first? trying to do this without removing carb so i dont have to resynchronize if possible. is it possible for the orings on the thermal valve to cause this? or gasket on top of carb?