By doing a search I know it is not possible do downgrade the baseband on the 3G, to date at least.
I have a legally unlocked 3g from Italy and the only reason I would like to downgrade the baseband is because 02.28.00 is the worst baseband the iPhone had to date.
It fluctuates between 3G and EDGE like crazy while other phones simply don't.
The baseband FW2.0.2 had was the best in my eyes.

From another post I found BBUpdatedextreme. I know you can use it upgrade only the baseband but is it possible to do the opposite and downgrade it instead?

Idly what I would like to have is FW2.2 with baseband 02.08.01.
Is it possible using the above tool?

Before you start to "downgrade" it (assume it is possible), just make sure that particular bb doesn't has that problem. My friend has 3G on 2.1 Bband, he has same problem like Others. Google it, something like, iPhone 3G problem. On some particular places,iPhone has "confusion" between 3G or 2G. As the result, the phone can't be use for In/ Outgoing call. Believe it or not it is truth.... The solution, simply turn off the 3G on that particular place.

Yes the 2.1 bb is also not stable. The most stable one for me was the 2.0.2 bb. My question is if it's even possible to run fw2.2 with the fw2.0.2 baseband and if the bbupdater tool is the way to go?