Is my turbo a VF39 or VF52 ?

Well if you have an 08 that's actually a TD04.

If you have the 09, then you have the VF52.

Here's how it breaks down

1) VF52 is essentially the same as the VF48, but with a different flange that bolts directly to the intercooler. The VF48 just has an open end that uses a hose clamp and tubes to connect to the intercooler.

2) VF48 is essentially the VF39 but with a revised, larger wastegate to help control boost creep.

3) The above two points mean your turbo is essentially a VF39 with a larger wastegate and a different flange to connect to the intercooler.

All the turbos mentioned in this post are stock on the vehicles. The 08+ models adopted the legacy gt layout, so now the intercooler bolts directy to the turbo. That's what I mean by the different flange. Look at your pictures and you can see that. The larger wastegate was something done by IHI to combat boost creep issues with the VF39, and they called the new turbo the VF48. There may be a couple other changes but that is the main one. Again, the VF48 is the stock turbo on the 08+ STi's, which is internally the same as the VF52, which is stock on the 09+ WRX. The only difference is the 52 has that flange that bolts directly to the intercooler.

In your case you have the TD04 turbo, just with that flange to bolt directly to the intercooler. Previous WRX's 02-07 had a rubber/silicon pipe that connected the turbo to the intercooler.

Look at post #18, side by side shot of the 48 vs 52. You can see the flange I'm talking about better.

http://www.wrxtuners.com/forums/f121/boost-addicts-08-wrx-project-24991/index2.html