don't know the diff between your 98 and an 03 Cobra, but Horsepower TV used a Hypertech Power Programmer on a bone stock 03 Cobra and the rear wheel HP went from 364 up to 407, an increase of 43 HP or 11.8% increase. after that, they replaced the stock pulley with 3" one and reprogrammed it again and the HP went up to 415 at the wheels. then they went with a 2.8" pulley and reprogrammed once more and got up to 427 rwHP. That ain' bad at all considering they barely got their hands dirty changing the pulleys out.

 

The 03's have a blower and the 98 dont