What do i need to change on my DCF model if it asked to ''Ensure that the DCF properly handles purchase accounting adjustments (e.g., double-check the Cash Taxes on EBIT calculation) ?''    

It's interesting.  They want to quantify their market share loss.  Meanwhile, one of the data items that you're given is the market share.  Sounds circular, right?  Are they saying that they know the loss in market share but they want to see how much is due to the competitor?  How did they gather the market share ...