Help Identify tube near manifold

[J Fender]

Have an 02 GTS, was changing the water pump after having the Viper for 4 years. Runs with no noticeable issue. While changing water pump noticed what appears to be a white vacuum tube or plastic line underneath the manifold on the drivers side. It looks like something was once attached. There is a capped vacuum fitting on top of manifold. Can anyone advise, thanks in advance. See attached picture.