It seems that the 109G-14 speed maybe off.
According to information established in this thread:
109 performance notesIt would appear that the G-14 is slow.
FTH for the G-14 should be 5000m (16400ft).
Here are the results of my level speed tests (see the linked thread others have confirmed them)
I just ran some quick level speed tests for the G-14:
AH2 BF 109G-14 level speed tests
100% Fuel, FBM = .001 (minimum; no fuel burn)
1 x 1 MG151/2cm 150 rounds
100ft
WEP - 350 mph
MIL - 320 mph
5000ft
WEP - 369 mph
MIL - 340 mph
10000ft
WEP - 379 mph
MIL - 357 mph
15000ft
WEP - 388 mph
MIL - 366 mph
16400ft (FTH?)
WEP - 390 mph
MIL - 370 mph
20000ft
WEP - 397 mph
MIL - 377 mph
24500ft
WEP - 388 mph
MIL - 378 mph
At 16400ft the AH G-14 only reaches a max of 390mph, this should be FTH and a max speed of 410-415mph 1.7ata 2800rpm). The AH G-14 reaches its top speed at 21000ft (just under 400mph).
568km/h (352mph) 1740ps @ SL
665km/h (413mph) 1700ps @ 5000m (16400ft)
This is supported by several sources in the linked thread:
First on MW's Spitfire site:
Spitfire Mk XIV versus Me 109 G/K A Performance ComparisonScroll down to the chart, look at the curve for the 109G-6/R2 (essentially a G-14)
Next Crumpp provided this:

Finally Kurfürst provided this (G-6/R2):

Note:
The speed curve (2) for MW50 max power, the climb curve unfurtunately only for 30-min Kamfpleistung 1.3ata. The rest of the data on the chart is basically the same as the doc Crumpp just posted. (Dashed 3) seems to show normal G-6 (or G-8 recce) performance at 1.42ata.