I replaced the fuel pump diaphragms twice in 2000 hours of running on my Pro-V 150 due to ethanol laced fuel pinholing the diaphragms. Same symptoms, bulb would go soft, hard starting and poor throttle response. Pretty inexpensive and easy to do.
That's where I'd start. Cheap. Easy.
As mentioned in my OP, only ever run ethanol-free gas, engine starts like a champ, throttle response is fine, just dies at idle.
