My X5 5-speed does the exact same thing. I've never tried to fix it because I know the cause and I've just never felt it worth the trouble to fix it. It's the off idle tip-in map.

I've had two e30s that did this exact same thing in the past. The first car was just an eta and it drove me crazy. I figured it was just an old car and running bad. When it was wrecked, I bought an "i" car and used the tranny from the eta to make the newer one a 5-speed. It had the same off-idle problem so I knew it was a BMW thing. I turbo'd it and put in big injectors, so I was forced to remap it. I used a Moates eeprom emulator and free software (I don't remember the name). But the definition file called the map "throttle enrichment" or something like that. Once I fixed that map, it was smooth as silk.

I'm pretty sure that BMW kept that map super leam to meet EPA regulations. Seeing as how there are so few 5-speed X5s out there, I figure the complaint level was fairly low. After the maintenance issues I had with a lowered, boosted e30, I had no desire to f-@k with my X5. I just want it to go long periods without breaking down any more. I hate sitting on the side of the road.