Just tried
--intensity 15 --thread-concurrency 8192 -g 1 -w 256
Still showing 20khash, Ive tried other intensities such as 14,13,12 and same issue.
Prolly need to wipe your drivers off cleanly. After uninstalling and rebooting, try the Catalyst 13.4 / APP SDK 2.9 combo. All my 7xxx cards love it.