hmm.. valve seal affects manifold pressure too, so yeah.. maybe the fueling might become erratic. but from what I know about speed density EFI systems.. the MAP (manifold air pressure) sensor almost entirely influence FC, with secondary input from the intake air temp (IAT) sensor and the 02 (which handles the final fuel trim).
Even a leaking intake gasket affects manifold pressure.. so that a good place to check as any for problems, before jumping into engine internals.
Your dynamic compression oso change what? could be higher/lower... why set to standard? (I assume you previously run advanced timing)
Running too high compression until need to retard ah? (O_o).. usually 12.xx - 13 compression require race fuel already.. or else, have to retard distributor quite a bit.