You are not supposed to relate any physical sensation (or feeling) to any sankhara for a good reason. Because in vipassana you are practicing to see the reality as it is. This is the keystone of vipassana, to see the reality as it is, in order to discover three characteristics of all phenomenon (i.e. anicca, anatta, dukkha). Trying to find the corresponding sankhara to every feeling and sensation distracts you from this and if you insist on doing it, after a while you will find yourself playing a mental game and you'll be running in the opposite direction of vipassana's purpose.
Moreover, I think quite different sankharas can create the same physical feelings. Also many a times a neutral feeling may arise because of physical conditions (how you sit, temperature, what you ate, etc.) so it's literally impossible to find an exact sankhara for each and every sensation.
Of course, on the other hand, if you're doing vipassana and memories arises, they should not be oppressed but simply you should let them come, observe them and calmly come back to the object of meditation.
As you progress your reactions in real life will show you how you've progressed and which sankharas has been eliminated and which ones still remains.