Seriously about to blow my brains out.

[bmrboi2]

2008 X5 3.0 si Active Steering

I have done some extensive maintenance on this thing and I am now faced with a vibration or shudder that is almost non sensical.

Plugs, Coils, Air Filter, Vanos cylinders, Sway bar links, Full Tie Rods, Front Thrust arms and bushings, Wheel Balance, Alignment, Belts, Battery, Pulleys.

At above 80mph I have a shudder/vibration. It lasts ONLY from 80-90 mph. 80-85 with the AC on. I have a slight vibration when making right hand turns at those speeds, that leads me to believe that the control arms or bushings are on their way out but I dont think thats the cause of the constant vibration.

It comes up when I am pressing the accelerator when Im about to head up a hill or even a slight incline. If I let off the accelerator the vibration is gone and everything leading up to 80 is smooth as silk, No shuddering or vibration. On flat roads its as smooth as glass if I am easy on the accelerator after 80 mph, moderate acceleration its there, full its gone.

Last week after some spirited driving I got a CEL for the Exhaust Vanos with the AC on and it went off and hasnt come back. I don't have my scanner at the moment (Its evaporated into oblivion) Whats driving me crazy is that I get no indication that there is anything wrong below 80 mph. Mat the gas down and she takes right off. Gentle acceleration and shes just fine. The only thing that I get on occasion after driving and the car is up to temp is an idle stumble/fluctuation upon restart and that lasts for a few second and everything is fine.

My gut is telling me I have a vacuum leak.....somewhere. I just don't know. Any help or guidance would be very very very much appreciated.