Our 88 didn't have the bulb/socket/switch but had the connector in the harness. Ours is also a late production car and go with the idea that they were just running out of parts so it was never installed.
I did add it several years ago, but in all honestly never really saw and need for it (or used it).
VIN does not show most options. You need access to GM VIN database that you don't have to get Build Sheet etc. Read RPO label.
Digging thru RPO data... TR9 Lamp group, courtesy consists of <-- From http://www.fierostuff.com/RPOcodes.html underline for a reason below... U25 Rear compartment lamp <-- trunk light U29 Instrument panel, courtesy <-- I think the "foot" lights
You find all of them and others on a car. Front compartment light could be in U25 or another RPO.
Note that: TR9 is could be same as MX1 for auto trans, MM5 for 5 speed stick, and others. MX1 is a "set" of MD9 (TH152c) and 1 Trans Ratio Code: F16, F17, F62, F75, FP3, FW2, FW9, F77, F79, or GX3 (Ratios covered in my Cave, Gear Ratio) TR9 might have some lights and/or is a set made up of U25 U29 and maybe others.
Other RPO lists TR9 is: Lighting, auxiliary Premium Lighting Package LAMP GROUP LAMP GROUP, COURTESY LP GRP
my 86 no sunroof, the light was not mounted and the wiring wrapped up---went to junkyard got the mount a bulb and it worked. my 88 no sunroof T-Tops, no light, no wires NO SWITCH--even my cowl has no hole for the switch--but I do have a trunk light according to the t-top registry my car left the factory 6-28-88 ------------------ Pat Jones
[This message has been edited by 88FieroGT TTops (edited 05-21-2015).]