High RPM throttle hesitation ..... any ideas?

I have a 2002 Chevy 2500HD 6.6L Duramax with 143,000 miles. Just lately I have noticed that when given more throttle in high RPM range (starting around 2800 rpm) the engine will stop excelerating and will hold in the same gear. I can let back on the throttle, it will then shift and then can excelerate till I get to about the same RPM again. It is like the engine can not get into the power band.

No Check Engine Light has come on. I have run atleast two tanks of fuel through and know it is not bad diesel. Any ideas???? Maybe fuel filter ..... I was going to try that when I get a chance.