Hmm, lets see...
Bf109E-4 - DB 601A - 1.3ata, 1100ps = 570kph@4.5km
Bf109F-4 - DB 601E - limited boost: 1.3ata, 1200ps = 640kph@6km
Bf109G-2 - DB 605A - limited boost: 1.3ata, 1310ps = 630kph@6.6km
Bf109G-6 - DB 605A - full boost: 1.42ata, 1475ps = 635kph@6.6km
Bf109G-14 - DB 605AM - MW50: 1.75ata, 1800ps = 665kph@5km
Bf109K-4 - DB 605DB - MW50: 1.8ata, 1850ps = 710kph@7.5km
The issues I can see are:
1. G-2 has to cover alot of time until the G-6 becomes useable because full boost(1.42ata) wasn't authorised until early '44 iirc.
2. No high-altitude model until the K-4. Either need G-14/AS or G-10 with a plain DB 605D.