Yesterday a p51 catched me in a circleclimb, and i took occasion to repeat my offline- climb tests.
I did  both measurements with a 50% fuel (no external fueltank), no wep, mk108, no gondolas, climbspeed 140 (autotrimm speed)
Here are the results, time for 3000ft climb in seconds
       109old  109new   ratio    P51
3000   45      52       0.86     54
6000   44      54       0.81     56
9000   45      55       0.82     56
12000  47      56       0.84     56
15000  47      58       0.81     64
18000  49      58       0.84     71
21000  49      61       0.80     74
24000  54      67       0.80     76
109 perfoms between 15-20% weaker now in the climb. That means about 15% less power.
I repeated also the measurement for the p51 to be sure that it is not the P51 that performs better now, but the results are the same.