Have you checked your dampers yet see if any of them are leaking?
It's could also be a suspension bushing issue. You said it was leaning all over the place in the turns, was the car loose at all?
Also if your having diff issue that could be a cause of loosing time. I would also go over the whole car, and check out everything before trying to band-aid it with sway bars which could lead to another issue.
My two cent is, I really like the Tein coils. Flex and Mono Flex, and the EDFC is awesome to play with. Though some racing syndicates won't allow you to run it on course, and I hear good things about their new EDFC active. You can also get custom valving and have them rebuilt here in the states when the time comes.
NISSAN 370Z