Yesterday My car threw 4 codes; 0400,0402,0171, 0174.
0400 and 0402 are EGR (comes up about every week cause i have no EGR...)
0171 and 0174 are banks 1 and 2 running lean. (never had that code before)
Car was running fine when the codes came up but started running weak (limp mode i believe). After i cleared the codes the car started doing this...
Revving problem video by huffster_2007 - Photobucket
Any help would be great, I'm thinking air leak maybe...

OH, p.s. the brakes have nothing to do with it. I was pressing the brakes because there was a car in front of me... just clarifying.

 

have you checked to see the manis are tighten down properly....first place to look for an air leak, then make sure every thing is in it's place, hoses, throttle body and such....my guess is the manis....

OK, watched the video...duh....not sure it is manis, since it goes to an idle....although the throttle body may be late in reving down if it is sucking air....

I have never tried this trick on a XF...I use to spray WD 40 to look for throttle leaks on the sports bikes and Harley...you might try this around the seals of the manifolds while the car is running....if it idles up, you are sucking air...leaning a cylinder, which will lead to burning a piston....I will let the others chime in....

 

I actually already tried that. I sprayed everywhere on the intake side of my engine. Not one pep of it idling up.