Depends.
Last month I had to have the Boxster done, I knew it needed tires and brakes since the last time four years ago. They flagged those, plus the front two blinker lenses, and the mechanic just signed off on them, no need for a retest.
One of my bikes failed for a non OEM brake lever, I found the 30 year old paperwork from the manufacturer, took it to the head inspector, who looks at eat, then back at me and asks "how old is this bike", shakes his head in despair for his young underling, and OKs it.
Tom
Oh wow, that's impressive on the detail.
So, hypothetically speaking... would adding a set of oil catch cans (made by the manufacturer, but not fitted as stock) require further paperwork?
Generally speaking, if the car is reasonably recent (under 10-12 years old) and well-maintained, you shouldn't have trouble passing the inspection. If there are minor issues, you will be told to rectify them and come back for re-inspection.
They are sticklers about cleanliness, though, so you stand a much better chance of passing if the car is clean inside and out, including the underside and engine bay.
If you want a lower-stress experience, you can also have the car inspected *before* being invited to the MFK by the TCS. This is not a pre-inspection -- if you pass, you're good to go for the next two years. The TCS also has an engine cleaning service, if you don't want the hassle/risk of doing it yourself.
This depends on the canton nowadays.
Many cantons authorise garages to do the repairs and report it as done, without a re-test by the MFK.
Zürich has introduced that recently, too.