I am currently taking of the front bumper to get the headlights out and redo the groundstuds with screw in the original studs with aluminum screws and cuttin thread through them. At the same time I am exchanging the wheel well liner / bumper shroud .
just found out .
Either later material from x358 is softer or it is because of age and miles my original one is way stiffer and cracked a bit anywhere.
x358 liner seems to fit on x350 after a minimal cutout on the lower front/ lower bumper area .
the other way around x350 on an x358 does not seem to work . Might be possible but would not adjust into behind lower bumper part that seems to have more outward shape

 

 

Hi Petz,
The bumper under covers for an X358 are a different shape to the X350 because the bumpers are different. The X350 bumpers curve underneath more, while the X358 has a more vertical bumper with the extra grill 'mouth'. My X358 bumper cover locks in to the rear of the bumper with grooves, which gives it strength. there are also a number of fasteners to the wheel arch liners. All are 6mm screws, some with a hex head, some as a t30 torx.

Pete M