Why is the F86 so slow?

[Raven Morpheus]

Hello

I thought I'd have a go in the F86 and so I downloaded the campaign called Honcho and CY6's Korea map.

However, having looked at Wikipedia I am left wondering why the F86 is so slow. The most I can get out of it is 630mph but that was in a dive from about 6000ft to about 3000ft. When going in a straight line at about 5000-6000ft all I could get out of it is 300-400mph.

Wikipedia states -

Maximum speed: 687 mph (1,106 km/h) at sea level at 14,212 lb (6,447 kg) combat weight
also reported 678 mph (1,091 km/h) and 599 at 35,000 feet (11,000 m) at 15,352 pounds (6,960 kg). (597 knots (1,106 km/h) at 6446 m, 1,091 and 964 km/h at 6,960 m.)

So why is the F86 in IL2 200mph-300mph slower than it should be?