How does one smooth out the snatchy throttle response?

Plastic explosives!!!!!!!!!! Seriously, have you checked out all of the linkages to make sure that there is no sticking during any part of its movement.

How about the fuel delivery system? Constant fuel pressure at injectors? Fuel injectors?

Assuming there's a sensor to the control solenoid, the sensor would've sent a trouble code to the ECM, activating your "check engine" light. When you accelerate, it increases pressure in fuel lines, so if there's restriction (such as dirty fuel filter) in fuel line, then it would accelerate rough with hesitation in throttle response.

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Cleaning the throttle body often fixes this problem otherwise you will likely need to replace the throttle control motor. At the throttle control motor monitor the clutch operation. Check to see if the computer is supplying the clutch circuit with a 12 volt square wave pulse signal. With the key in the on position, check to see if the throttle motor makes a buzzing noise as the throttle is opened and closed. With the key off, push the throttle plate open with your finger and allow it to close. The throttle plate should open and close smoothly.

You need to run a fault code test on the ECU. here is how you do that.

Most likely the rocker shaft end float that needs to be adjusted.

Check your clutch plates, it may be slipping at higher RPM on low gearing but have enough contact area on lower RPm higher gearings. Good enough to rate this advise?

Recheck that carburetor was assembled correctly and that fuel lines, including the one in the fuel tank, are in good condition. Preset the H & L needles at 1-1/2 to 2 turns from stops. Check for good spark on the spark plug. Check air cleaner and pull muffler apart to check for plugging. If will start and run, set H needle so that engine 4-strokes at speed, but smooths out when cutting wood. Set L needle so that engine idles fairly smooth, but allows engine to accelerate rapidly with throttle. Idle speed adjusted to keep engine running, but chain stopped.

sounds like u need to do a tune up on it. clean the carb, new plug