Didn't you get rid of a Zetec for the Duratec?
The if your zetec makes the Duratec feel slow, then that car has some issues, and if you're going to be re-building the V6 anyways why not add the "goodies" while your at it.
Also, if the zetec is being more reliable, wouldn't it make more sense to keep it as your daily driver?
Though for the money you'd spend boosting either of thoes cars, and considering their mileage I'd sell both and go buy
this. 
