The -30W was upgrade, not downgrade. More knowledgeable people will know more about the reasons why the -30 was more powerful than -34W, however the altitude power was 1600 HP at 22000 ft for the -30W, vs. 1600 HP at ~18200 ft for the -34W. With water injection, the -30W was capable for 1800 HP at 23250 ft, compared with 1850 HP at 15500 ft for the -34W.
No wonder the F8F-2 was considerably a better performer.