Welcome to the forum my fellow D23 owner.
I would defiantly make sure the car is sound in the engine, and suspension aspects of things first. Well how long have you had it for? 3000 miles, or 10,000 miles?
And if you want to talk modding the D23, that's no problem. But I got a few questions first.
1. How many miles on her?
2. Auto or manual?
3. Tach or no tach?(should have a tach)
4. is there any bad service history that you know of?
5. is it a PZEV or not?
6. what year is it?
And you will see in my signature our " How-to directory.
", it has some visual mods, and some maintenance procedures in it for the focus and other Ford models.
but we also have a performance section too, there is not much in there cause I've been working on the how-to directory, but it has the basics atleast. Focus performance FAQ's.
It even has the focus suspension spec's for if you want to lower her.