XC70 Delayed Acceleration

Greetings,
I am new to this site and I was unable to find anything about this issue so far. I have seen comments about delayed acceleration from a stand still, but that is not the case with my car.

I have a 2003 XC70, Automatic, 5-Cyl, 2.5 L Turbo with 80,000 miles on it. I bought it new. The problem is delayed acceleration after the car is already moving. It seems to be when it is shifting gears. With even pressure on the gas peddle, the RPM's will increase but the car will not accelerate until about .5-1 second later, it will finally catch and accelerate.

This problem has happened from the time the car was very young but it is happening now with more frequency. I told the Volvo servicemen about it everytime I brought it in for regular service but they could never find anything wrong. The problem does not repeat itself on a regular basis so I could not show them in a test drive. All they would do for me is check the computer for any errors and, of course, there were none. I'm bringing it in again for service on Wednesday so I hope someone might know what the problem could be so I can suggest it to the Volvo servicemen.

Thank you,
Peter