I would not go tearing into the engine unless you certainly know you need to. The fuel trim issues could be unrelated to the IMS tensioner pad.

 

@MOWMOW If I'm understanding the first post then they had at least the heads removed initially to replace the Variocam actuators and guides, and now they want to completely disassemble the engine on a second go-around? I'm not asking to count your money but I'm imagining you're in pretty deep already - and they want to go deeper. Do you have any access to another shop you can take this to for another opinion? The first post sounds like a witch hunt and the second sounds like they finally found the issue. EDIT: or another issue.