Wait a second.
My source mentions 2 speed values. The second one is with wep, 1.42 ata and 2800rpm.
With wep the 109f1/2 did 615 km/h at 5.2km (about 16500feet), what is 384mph. On the deck it did 321mph. Its with the 1150Hp DB601N. It sounds real while the 1350Hp E-4 can do 395mph at alt, 333 on the deck.
Without wep (1.30ata, 2500rpm) it did 309mph on the deck. SO... with all the aerodinamic improvements, the F wasnt faster than the E with the same engine??
I think your Emil source shows the DB601N with 1.42 ata, what sounds more possible, around 12-15 mph difference.
Btw. The E-7 would be a great match against the Spit5, what its real opponent was, while the E-4 was in the same era as the Spit1.