Pull the air box resonator. put in a K&N drop in filter (and or upgrade to a Stock SVT air intake box with a K&N drop in filter.
Suspension go with a Ford Racing Performance Package... basically is the SVT suspension.
Their are lots of stickies that talk about what all you can do to mod and how to do it. Their are also lots of build threads to see what people have done and are doing.
What are you looking at trying to do for the car? want it to be fast in a straight line? want it to be a zippy little car that jumps in and out of traffic? How much are you wanting to put into the car?
Any product that the sponsors of this site sell are good brands.
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)