I've seen Bob's car multiple times. I not sure that even the most discerning Mark II enthusiasts would be able to tell it wasn't 100% stock/authentic from the exterior and most knowledgeable car folks would only be able to tell it wasn't stock under the hood when they recognized the master cylinder isn't period correct.
Given the reliability factor, I'm sure Bob has impacted the value of his car: it's worth more than it would have been without his subtle modifications.