These lifters may not be OEM manufacturing. I have performed over a dozen lifter installs with dealer supplied parts. Immediately after installation within the first mile the MDS lifters failed, and caused check engine light and rough running on cylinders #1 and #7. For testing purposes I removed the head again and installed original MDS lifters back to cylinders #1 and #7 (I originally sought to remedy a very faint lifter tick developing). Upon retest the concern of those specific cylinders was remedied, THOUGH Cylinder #6 now shows fault and the engine is running rough.
I will be removing both heads (again) and replacing the lifters with parts purchased directly from dealership to ensure my customer all adequate steps have been taken to ensure a precise fix on concerns.