not having your suspension properly setup will give you really bad headshake when doing turns. before i got my suspension setup correctly almost every corner id come out of accelerating hard my front end would wobble untill the bike was completely straight up and down.

another thing to think about is body positioning, from what it sounds like you were riding improperly.. then once you got the slapper going you decided to secure the bike with your legs/knees. you shouldnt wait till this happens, you should always be riding with your legs/knees/ankles grabbing onto the frame. this makes the bike MUCH more stable throughout everyday riding and esp at speeds.

another thing, when getting a tank slapper, speed wobble ECT you should have a FIRM grip with your legs/knees but have a LOOSE upperbody. your bikes frame/suspension is some high tech shit, as long as YOU are positioned properly and keep a steady throttle it will work itself out.