Kind of hard to describe; '02 S80 T6. Occasionally I like to “boot it” and feel the power available from this engine. In most cases it pulls nicely through the RPM range (it takes some control to keep the tires from spinning initially). Occasionally (and it seems like it does it more when I'm turning from a complete stop but also does this on the straight away) that the engine hesitates or bogs momentarily at about the first gear change then recovers and carries on accelerating with plenty of power and no further hesitations. It does not occur if I shift manually - RPM's climb smoothly. It does this with or without the DSTC. It does this only under full or near full power – anything less and the symptom almost disappears. It doesn’t happen all the time – but about 50%. I can’t tell if it does it at exactly the shift from first to second when in auto but it could be. I changed out the boost control valve – no difference. No codes or messages. Any ideas?