Seeing a lot of confusion in this thread... a few things:
The 2.3.340 .sbf that's floating around, is a system only .sbf. There isn't a full .sbf available publicly that I'm aware of... (If there is, please send me a link!
Since you stated you were on 1.8.9 of Focused, that means you are still on the 2.3.15 bootloaer (30.03, or the 30.04 that came on some replaced phones), BOTH can be .sbf'd back to 2.3.15.
Once you get the phone back to 2.3.15, you can load the OTA in two ways... by pulling it over the air, or by downloading the update.zip. (Note: update.zip is the same file that gets downloaded and installed by the OTA).
The 2.3.20 text in Focused 1.8.x is just that, a line in a file (build.prop). Drod (Focused dev) put the line in, because some of the components of the ROM were based on the 2.3.20 build. So there aren't any issues going from 2.3.20 to 2.3.15.. You're on 2.3.15.
So, to get to the OTA (2.3.340), or the leak (2.3.320)... **should** be as simple as .sbf'ing back to stock 2.3.15, and then either loading the OTA (either way), or following the leak instructions if you prefer the leak to the OTA.
HTH!