wheee!

All of the above are negotiating points. You may not be able to do anything about the older steering lock or diff issues (if it has them) other than try and get a price reduction in line with the wear/tear etc. The ecu whine is a high pitched whine, noticeable at idle by some people. I never had it with mine. There is a TSB for that though.
The diff leak indicates an abused car. That in turn indicates possible problems for other parts you can't see....

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