are you sure everything on the wishbone is bolted up propperly?
i had EXACTLY the same problem and i checked everything over.
In the end i brought it to a garage and let them check everything over again.
In the end it was the wishbone bolt that was tight but the thread was worn.
The garage rethreaded it and all was good.
The bolt i am talking about is the one you bolt up an lower arm bar to.
