I'll jump in & listen for answers... Mine (a 3.0 with manual trans) does that on occasion as well; when accelerating from a stop, usually just before shifting to the next gear, it's like somebody stomped on the throttle and it jerks forward. It only lasts for a split second because it comes on just as you start to depress the clutch, and is done before you can do anything else to see if it keeps accelerating. It happens right around 3000 rpm, and only does it on that first shift, never on subsequent shifts.

I doubt it's a vacuum leak; just replaced the intake boot, and checked for other vacuum leaks while I was in there. Could be the DISA valve; will check that. I was also wondering about VANOS; CEL is on, but I haven't had the codes read yet.

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2001 X5 Sport 3.0/5-speed
1998 318ti/5-speed
1988 735i/5-speed
1984 528e/5-speed (soon to be M20B25-powered 525i!)