For a guide on how to flash a modem to your gs2 please see here
http://androidforums.com/galaxy-s2-international-all-things-root/588852-modem-installation-dummies-guide.html#post4715017
Lp6 modem available from here
http://developer.clockworkmod.com/downloads/51/1855/radio-cm-9-SGS2-LP6-signed.zip
Just about to flash it so will report back in a bit.
http://androidforums.com/galaxy-s2-international-all-things-root/588852-modem-installation-dummies-guide.html#post4715017
Lp6 modem available from here
http://developer.clockworkmod.com/downloads/51/1855/radio-cm-9-SGS2-LP6-signed.zip
Just about to flash it so will report back in a bit.