That is a very nice looking '86 sedan, when did that join the fleet?
I found the instalation of the one piece vent cover on the '80 quite simple, and it fits very well. The twin small covers for the '92, well that was another story. I covered the end of a screwdriver with masking tape as the instructions suggested but was not able to get them on; think I was nervous about doing something that might scratch the paint. The car was going into the shop a couple of days later for something so I wimped out and left the vents and the modified screwdriver in the car and asked the shop install them. There was no separate charge listed for that, and vents are fitting well and very snugly. I think if I had to I could remove the older one-piece cover, but I think the others are on there for life!