Got my 7970 running again by lowering intensity from 13 to 11 and increasing TC from 8192 (--thread-concurrency 8192) to 10240 (--shaders 2048).
Same worksize 256 and same g 2 and same --lookup-gap 2.
Deleted the bin files before starting yaminer.

Reduced hash rate by over 60%, so there is a lot more tweaking to do...

Pool went from 35Mh to 7Mh, guess all GPU's got killed by the N factor.

EDIT Still getting HW errors, trying lower intensities