If you are looking for a fast ROM with good battery life, here’s Paradox ROM you can try out for the T-Mobile Galaxy S2 SGH-T989. Although Paradox ROM supports overclocking, it feels super-fast even at default 1.5Ghz speeds, I think this is one of the fastest ROMs without overclocking. Which means you can get great battery life and performance.
I will have an update on this ROM in the near future but in the meanwhile try out this ROM and let me know how it works for you.
Download ROM here:
Download Paradox ROM
Credits and Donate to ROM Developer Here