I was inspired by another post of similar name, such that I thought I'd throw this out to the community.
Here are mine...
Dear Previous Owner,
I really wish you hadn't let CarToys "install" a new head unit and speakers and allow them to cut the power and speaker harnesses, especially when adapter harnesses are cheap and readily available.
Dear Second Owner,
I hope you didn't pay that amateur much to wire in that radar detector back in ~1989.
Dear Previous Owner,
I'm glad you installed a 993 style convertible top. I wouldn't have had the guts to go non-original and you know what? It is a much cleaner design. I prefer the look...