Dead at 60!

[rgpjr]

OK I know this issue has been beaten to death but I need to figure my best course of action.

2001 S80 2.9

I am getting the surging and hesitating issue that everyone blames the on ETM. The funny this is the hotter the weather the worse it is and it is intermittent. The weird thing is that on the highway if I am going 50MPH or under or anything over 70mph it rarely happens. But at 60mph it all but dies (feels like a hesitation and will drop 5-10mph before surging back to speed), if I floor it (or give just a bit more gas) it hesitates then accelerates. On occasion it does this same hesitation / surge from the line like from a stop light. Like I said, its not an everyday thing and some days are worse than others. I have absolutely no issues with idle, its as smooth as a baby's butt sitting still.

Would you still suspect the ETM or would you try cleaning the MAF first or any other suggestions?