For a 401(k) plan when determining top heavy determination do you have to add back to the ending balance the prior 4 years plus current year distributions, pre-EGTRRA rules?

maybe. it depends on when the terminee quit.
suppose he quit 20 years ago and received his distribution this year. would you include that distribution?
remember, under the old rules you exclude balances of those who have not performed service for 5 years as well. Just because someone finally receives a distribution doesn't mean you start counting it again.