Welcome to the forums Patrick,
Now without sounding like a complete downer, don't do anything to a csi. You Csi would be a 4afe i presume, an engine that isnt particularly modifiable.
You best bet would be to keep the csi clean and tidy, eventually sell it and buy a 4age gti/sx corolla. You will make more stock power than you would doing any mods to the 4afe.
If you really wanna do a few bits and pieces, get a K&N or BMC washable panel filter for the stock airbox. don't get a cheapo brand and they arent washable/oiled properly, nor do they do much in the way of airflow/ filtration.
There are some body kits available, however (imo) they look dodge, but again its not my car. Those kits are on ebay, but i don't remember the other website. Otherwise Putting SX bars onto the car + plus a lip (MX73) will improve the look considerably.
Example:
The day i got my first car:
And the day i sold it:
Small yet effective mods.
Bugz.