do you need one thats for you to decide. I have an 04 and run a fuel pressure gauge, a boost gauge and the pyrometer. I also have a scan gauge to monitor the engine water and oil temps. Highest egt I have seen was about 1350 for a few seconds. The fuel pressure gauge is important as the pressure determines the life of the injectors, a blue spring mod ensures positive pressure to the injectors. The water and oil temps indicate possibility of a egr/oil cooler issues. Yes even stock engines need to be monitored, but again its up to you.
A scan gauge can be gotten for around $130 at most auto supply, glowshift gauges can be had in 3 or 4 groups and are relatively inexpensive gauges that work well. I think 3 pod gauges can be had for around $150 or so check their website.