To check Cook's distance by the centered leverage value,
recall the Simple Scatterplot dialog box.
Deselect Standardized Residual as
the y variable and select
Cook's Distance
as the y variable.
Deselect Zscore: Wheelbase as
the x variable and select
Centered Leverage Value
as the x variable.
Click OK.
The resulting scatterplot shows several unusual points.
To identify the points, activate the graph by
double-clicking on it.
Click the Point Identification tool.
Select the points.
The point with the largest Cook's distance is the 3000GT. It does not
have a high leverage value, so while it adds a lot of variability to
your regression estimates, the 3000GT did not affect the slope
of the regression equation.
Similarly, many of the cases with high leverage
values do not have large Cook's distances, so they are not likely to have
exerted undue influence on the model.
The most worrisome case is
the SL-Class, which has both a high leverage and a large Cook's distance.
This vehicle has a large wheelbase and price tag, so its influence is related
to the problems you observed in the residual scatterplots.