Power loss at high speed, lay the throttle off, seems to run ok at 50 and below, anything over and it starts to loose power .seems like fuel starvation ?

Your coil problem, change with the new one.

After reading about Honda's Eco Throttle system available on inverter generators it seems it is not a fuel metering system but a computer controlled speed regulator or basically an electronic throttle.
Because the engine of an inverter generator doesn't need to run at a constant high speed to produce the correct 50 or 60 Hz output this generator can run at slower speeds when the load is light. The electronic throttle is the means to make it happen - operated by the computer.

The throttle is probably operated by a stepper motor and the power supplied to it likely to be in digital form. I suggest you try and gain a more full account of how the system works before you delve deeper.

It sounds like the high speed passages in the carb are gummed up. If you have not done so already, you should probably rebuild the carb.

Since you changed the sensor we will assume it is working. When you disconnect it you put the computer in limp mode which stops it from using sensor values. If code 300 is the only code we will assume the coolant temp sensor and others are ok.
I would check fuel pressure with a gauge next.

if the exhaust blows black when this issue starts,then probably a bad regulator,which the check engine light will come on then go off a few times telling you a code,oxygen sensors...if not,try replacing the throttle position sensor,its tough because its at the bottom of the throttle body,and the screws rust in and sometimes breaks,so the throttle body has to come off.you have to figure out where the gas smell is coming from at least,it could be blowing back into the air breather.also check the vacumn lines(green hose and red hose) on top for cracks.the red should be for the regulator

you need to make sure there is not a fuel restriction first check the fuel filter, then the lines. If these seem ok then adjust the High speed rpm, there should be two adjusters one for High speed one for low speed(when the throttle is fully engaged.Do small adjustments at a time.

Inspect Wireset Damaged, worn, or deteriorating spark plug or coil wire(s). in this list u will find a answer to ur problem Shaun 2 Inspect Spark Plug Fouled, damaged or broken spark plug(s). 3 Inspect Fuel Filter Clogged or dirty fuel filter 4 Inspect Distributor Worn, loose or incorrectly adjusted distributor. 5 Inspect Distributor Cap Loose or cracked distributor cap 6 Inspect Distributor Cap And Rotor Kit Loose, cracked, or worn distributor cap and ignition rotor. 7 Inspect PCV Valve Plugged or damaged pcv valve. 8 Inspect Air Filter Restricted or clogged air filter. 9 Inspect Catalytic Converter Clogged, damaged, defective or faulty catalytic converter. 10 Inspect Automatic Transmission Improperly adjusted kickdown cable adjustment or internal transmission problems. 11 Inspect Fuel Pump Improperly functioning fuel pump or circuits. 12 Inspect MAP Sensor Improperly connected or faulty m.a.p. sensor. 13 Inspect Mass Air Flow Sensor Improperly connected or faulty mass air flow sensor. 14 Inspect Throttle Position Sensor Faulty throttle position sensor or throttle position sensor circuit. 15 Inspect Timing Specification Incorrectly adjusted engine timing. 16 Inspect Fuel System Pressure Incorrect fuel pressure being delivered to carburetor or fuel injection system.

the inside of the prop has a rubber between the prop itself and the inside splines to act as a shock absorber,say if you were to hit a rock. that rubber had spun out and the splines are turning inside the prop. the prop is screwed. seen it 100 times before.