My sister's 2001 Escort 4 door had a CEL last week and it ran bad. They swapped out the whole cylinder head. But, it's not a Zetec, it's the 2.0 SPI 8v.
The CEL light came on again! She wanted to trade for a Focus, but I said take it back (Landmark Ford) and make em fix it! If she decides to get a Focus, I'll look for one with a Z. (Has to be a 4 door, sorry Phil)