2008 4 stroke 150 runs poorly

[Preston Beal]

My 2008 150 four stroke on my pontoon, runs poorly. Will start o.k, and idle o.k. slow accelerate and speed up o.k. When I slow down the motor will usually die. Acts like the choke is stuck (though it doesnt have a choke).. Need to high idle to restart, and then will bog on acceleration. Shows a gas ring on the water when idling. Pulled and replaced the plugs. They were all carboned up, black and dry. Installed new plugs, same problem. New gas, gas treatment. It seem to use excessive amounts of fuel (used about 20 gallons to go 20 miles at different rpm ranges from 1000 to 5000). Boat was operating at sea level , and is now at 3500 feet. Any ideas.

[99yam40]

need to get it hooked up to a computer to see what everything is doing.
Too many sensors to guess and throw parts at