I had a similar question in relationship to the CFAI materials question, Prob #1 Reading #40. The schweser problem states that the company issues new senior debt. Issuing new debt will increase net borrowings which only impacts FCFE, not FCFF. However, in future years, interest expense will be higher and, since the FCFF formula includes interest expense - the initial reaction is that FCFF should be adjusted higher in future years.
While FCFF does add back in interest expense, the interest expense itself will decrease Net Income by exactly the same amount. So Net Income is actually lowered in future years by the increased interest expense, however, the FCFF formula adds this interest expense back in - resulting in zero change. Credit goes to the guys who answered my question in the forums posted today.