I'd like to voodoo lagfix my phone, I'm currently on the latest 2.3 official firmware - can I do so without going back to a previous version of the firmware?

If not, is there a way I can go back to a previous, compatable firmware version, apply the voodoo lagfix, then install the official 2.3 firmware from Kies while keeping the voodoo lagfix?

Apologies if this has been asked before, I couldn't find this specific question in other posts.