The value of $$\tan 9° - \tan 27° - \tan 63° + \tan 81°$$ is ______.

We group the terms using complementary angles: $$\tan 81° = \cot 9°$$ and $$\tan 63° = \cot 27°$$, so the expression becomes $$(\tan 9° + \cot 9°) - (\tan 27° + \cot 27°)$$.

Using the identity $$\tan\theta + \cot\theta = \dfrac{\sin\theta}{\cos\theta} + \dfrac{\cos\theta}{\sin\theta} = \dfrac{1}{\sin\theta\cos\theta} = \dfrac{2}{\sin 2\theta}$$, we get $$\dfrac{2}{\sin 18°} - \dfrac{2}{\sin 54°}$$.

Substituting $$\sin 18° = \dfrac{\sqrt{5}-1}{4}$$ and $$\sin 54° = \dfrac{\sqrt{5}+1}{4}$$, this becomes $$\dfrac{8}{\sqrt{5}-1} - \dfrac{8}{\sqrt{5}+1} = 8\cdot\dfrac{(\sqrt{5}+1)-(\sqrt{5}-1)}{(\sqrt{5})^2-1^2} = 8\cdot\dfrac{2}{4} = \boxed{4}$$.