2001 S80 T6 surges, stutters, hesitates, stalls

[oldtimertoo]

Hi Guys. I have an S80 T6 that I can't figure out what is wrong. The car just passed Calif. smog with flying colors, shows no codes, starts, idles and runs at low speeds perfectly. However, at any steady speed it acts like the ignition is being turned on and off rapidly-just sort of stutters along is the best I can describe it. Under medium throttle acceleration it hesitates and surges. Under hard acceloration it will leap forward, go dead, surge forwad again, hesitate, surge forward again. Sometimes goes totally dead until you lift your foot, then comes right to life. I had similar problems with my 850R and it turned out to be the MAF, so I replaced the MAF, but it didn't help at all. With no codes I don't know which way to go. Has anybody else experienced this? Does anyone have any ideas? Any help or thoughts would be greatly appreciated!! Thanks