Hi John: I just found your post, and while I never saw the post you are looking for, my first thought as a retired mechanic deep into models, that the first thing to do is remove the spinner on our plane, and see how the engine runs. Could be an engine problem rather than a spinner one. From my readings, a spinner directs the airflow towards the blades, and stops the turbulence created by the firewall.

Get back to me how the engine runs without the spinner.

Cheers!!!

Rich