two questions

Hey Is it expensive to replace the flex pipe on a 97' 2.2 Liter. Also what is exactly different about the Rally Sport Model, that is what i have and it doesnt seem like any difference other then ugly head rests and pink writing on the side. haha..

nothing is different, its not even a car made by GM, its a dealership scam to mark up the price and think you got some kind of sport package.

Exaclty what -Jayson_ said! The put that modling on the car and i think you got those ugly alloy wheels. Then the mark the price up a few Thousand bucks.

Rally Sports were factory models, not dealer models. However, they pretty much were just stickers and headrests, rear spoiler. They were all 2.2 OHVs, but you could dress 'em up how you wanted. I've seen some with the 15" aluminum wheels instead of the 15" hubcaps, some came with tachs, etc.
I had a '99 base model coupe that I bought brand new, not marked as a Rally Sport anywhere, but my insurance cards indicated Rally Sport due to the VIN number. Others I've talked to tell me the same thing.
To make a long story short, they're not really special.
Here's a couple links to reviews of the '99 model year, where the Rally Sports are listed right along with the base, LS and Z24.
http://www.autoworld.com/cavalier.htm
http://www.internetautoguide.com/reviews/1999/1999_Chevrolet_Cavalier.html (http://http://www.internetautoguide.com/reviews/1999/1999_Chevrolet_Cavalier.html)
http://www.intellichoice.com/reports/vehicleReport.cfm/vehicle_nmb/100015995/year/1999/make/Chevrolet/model/Cavalier