If your looking for mods, i know a few sites you really do need to check out then.
First one is www.crownvic.net
, my friend is on that site with his marauder and it is a nice forum, lots of information.
Secondly, check out www.adtr.net
, Chris (known as rocketcouch on cvn) has aton of stuff that will fit your sport. The most popular mod with a vic is the "MZT" Or Marauder airbox, 80MM MAF and a tune from lonnie at blue oval chips (http://www.blueovalchips.com/
That alone will make your crown vic really move.
Alot of vic owners like to put in an LSD or a posi with 3.73 gears, for those nice 11 marks and not a 1 wheel peel, plus the 3.73's make it get up and go alot quicker. Or 4.10's if you really want to move.
A J-Mod to your 4R70W transmission is something else that will make it shift very firm, but the tune alone will do that also.
Lots of other modifications you can consider would be replacing bits and pieces of the exhaust, kooks headers, underdrive pullies, a ported plenium and throttle body (adtr does this) addco sway bars and metco control arms (if you want your car to handle like its literally on rails)
I believe since you have a Sport, it has the handling performance package and the dual exhaust, which is the same piping as the marauder exhaust minus the mufflers and tips.
Good luck with your car, and have fun browsing those sites, its always fun to have a fast vic, because it always surprises the person at the light next to you that they just got beat by a grandpa's car