2006 XC70 Power surging, MPG plummets

[xtopha]

I was experiencing surges in power and noticed the average MPG had gone down to 16.8. According to forum advice I disconnected the battery for 10 mins and tried again, still surging. Next time i remembered to put key in position 2 before reconnecting. Problem seems solved, no more surges and avg MPG is up over 20!!!
I see that someone posted that this only lasts 4-500 miles. We'll see. But the re-set is no big deal.
Oh, and the dealer said that the Volvo extension of the warranty for MAF runs out after 10 years or 120,000 mi. (I'm at 125,000)