Changed the fan clutch and the power has been restored when accelerating.

One of the checks is that at idle, revving the engine for 10 seconds or so should result in the fan clicking off.

P0303 and Fan clutch were two separate events and unrelated as far as I can tell.

Thanks for everyone's help.

 

Sounds good. Glad you got it figured out! I assume that having power back corrected the odd shifting, yeah?

Hopefully you don't have that code come back. Could still have a separate issue there from what you were saying.