Delphi is about as good as it gets in the "reliability" department, so I'd personally be inclined to look elsewhere. If I remember correctly, this condition can be cause by: Engine overheating, clogged/dirty fuel filter, ignition timing, vacuum leaks or wrong vacuum line routing, bad EGR valve, fowled plug(s), weak battery, a bad spark plug wire or two, and maybe another thing or two I can't think of like overheating ICM.
Where did the EGR valve come from and what brand is it? Unlike Delphi, just about everything is made in China by the lowest bidder using the lowest quality components on the market supplied by... CHINA! ...or is a Chinese counterfeit. Even reputable "Made in USA" brands are moving towards "Chinese Junk" status and can't be taken at face value.
There is no guarantee that a brand new component will provide years or even minutes of service, so don't immediately rule out that new EGR valve.
I'm not sure about the v6, but with the v8 the temperature gauge and the temperature the computer reads come from 2 different sensors. You could be overheating while the gauge is reading "normal". Might not be the same with the v6, just thinking out loud here. An indication of overheating would be "sluggishness", and I'd suspect you'd have noticed that and would have said something. ...unless you drive like Grandma that is.