From around the year of my car (a 92), every DeVille I have seen has pinstriping. Was this a factory standard feature, or does it just happen that every one Ive seen has had it done aftermarket?

my 90 has it, as far as i know it came like that. But i have seen some without it, it may have been an option.

It's standard. I'm not sure if there was a delete option though.

The Touring Sedan didn't have it.

It was standard on all except the Touring Edition, BUT it could be deleted (as I did) by ordering sales code D83 "Exterior Paint Stripe DELETE" ~ Between 1989 & 1993 it was deleted on between 24 & 29 percent, with an average of 26 percent delete ratio.