i have a 03 and was the last year for that body style. mine tops out at 106 and then the governor kicks in. yours will take longer to get there because i believe the 03s had the transmissions juiced up a bit.
The majority of GM vehicles have a speed governor that's set at 108 mph, some high performance GM vehicles may not have a limiter set on them. On my 2000 the speed limiter has been deactivated and will peg the speedo at teh 120 mark. I've had the car up on a Chassis Dyno and they actually had it spun up to 128 mph and still the tachometer was a few hundred rpms from redline.