Downgrading w890 R1FA035 to R1FA030

[senter]

Use these files:

1. W890_R1EA033_MAIN_GENERIC_AK_RED52
2. W890_R1EA033_FS_FRANCE_RED52
3. W890i_1204-5401_R2A_Customized_FR_France

Then update with SEUS to last version R1FA035.

"Problem is that now the phone drains battery MUCH faster than before the upgrade." - just stop 3G from here:

Menu > Settings > Connectivity > Mobile networks > GSM/3G networks > Only GSM

[Bingo]

Use these files:

1. W890_R1EA033_MAIN_GENERIC_AK_RED52
2. W890_R1EA033_FS_FRANCE_RED52
3. W890i_1204-5401_R2A_Customized_FR_France

Thanks a lot !

Then update with SEUS to last version R1FA035.

Not if I only want to downgrade, right ?

"Problem is that now the phone drains battery MUCH faster than before the upgrade." - just stop 3G from here:
Menu > Settings > Connectivity > Mobile networks > GSM/3G networks > Only GSM

It's already in "GSM only" mode.
In fact, it's in the exact same configuration as before. GSM only, bluetooth on with energy saving (I have a bluetooth headset), brightness minimum.
I'm serious, I really triple checked the phone's settings, and they are just as they where before (and furthermore I believe that I had brightness not set to minimum when running on R1FA030).

A google search on R1FA035 performance seems to confirm that there was indeed some performance tweaking in this firmware.
I also find that the phone is more responsive now than before (but that is hard to quantify).
For instance, browsing very large playlists while playing music was really slow on R1FA030, and it's quite OK now.

Anyway, I really don't want to trade battery life for performance. I'd rather have a very laggy but long running walkman !

Doesn't this seem plausible to you ?