Yak-9U's don't have the oil coolers under the nose either. In fact, they look so similar to Yak-3's, I have no idea how to tell them apart at a distance. I'll post some screenshot links in a moment.
The major difference is the -9U is notably faster, but not quite as agile.
Addendum: Ok, so I was going to try to get photos uploaded, but apparently Multiply is broken at the moment. So if you go
here you can see a side drawing of the -9U, showing how in that model, the oil coolers have been moved to the wing roots, and the radiator has been moved further aft, when compaired to the earlier Yak-9 versions.