Intake plenum

I know I need to change my LIM gasket pretty quick. I have noticed a few posts on here that the Plenum itself should also be changed. Can anyone explain why? 2002 GT. 82,000 miles.

Thanks

I believe this issue may affect your year model: this is an issue with an exhaust gas tube coming up thru the plenium, causing excessive heating of the immediate area around it, in turn which caused a reaction between the coolant and heated plastic and making the plastic age and crumble away, allowing coolant to be sucked into the intake plenium around the O rings.
I have a 97 Bonneville and had this issue last fall, 126,000 on the car. While my son was traveling to a funeral in it, the motor locked up. Thankfully, it was a case of "hydrolock", where enough coolant got into a cylinder to lock the motor up.
That being said about my Bonny, my son's 02 Gran Am has the same plenium as mine, but we have yet to have an issue with it. You probably have the same, as well.
Repair is relatively simple, if you have half a brain. I..... don't. However, I did manage to repair mine, after making 5 or 6 major mistakes. (i ended up pulling both heads and having them checked. The 1st time i tore the plenium down, i did not pay enough attention to it and simply reinstalled it with a new gasket. When the engine failed to operate correctly, i assumed the heads. Nope......a $139.00 new plenium, a new egr tube and some J-B cold Weld. suprise!!)
Get a manual from the parts store, @ $20.00-25.00 bucks and it will walk you thru the process.