1988-1996 Pontiac Grand Prix
Ground-Effects Kits

GM's factory ground-effects are among the best and cleanest looking you can get. The ground-effects on the high-end Grand Prix's have always been nothing short of stunning. It should be possible to add factory ground-effects to any low-end Grand Prix. This would require getting ahold of the ground-effects on the sides and doors, as well as new front/rear bumper covers. These parts can be found for the best prices at auto salvage yards. They can also be purchased brand new from any GM dealership.

1989-1990 Grand Prix Limited
1991-1993 Grand Prix GT, GTP
The 1989-1990 Pontiac Grand Prix Limited (turbo model) and 1991-1993 GT, GTP had the same side ground-effects and rear bumper, but the 89-90 had a different front bumper fascia due to the composite flush-mounte headlamps. The 91-93 used the mini-quad headlamps. The 1994-1996 ground-effects were similar to the previous model years, but was rounded off for a more contemporary appearance.
1994-1996 Grand Prix SE, GT, GTP

Ground-Effects kit from Erebuni Corporation Style 103.

Erebuni Corporation has a complete ground-effects kit for the 1988-1990 Grand Prix 2-door that has vent-looking things on the sides. This kit is not compatible with cars that have factory ground-effects. I believe it is an A&A Specialties brand.
Erebuni Corporation, Style 103.

Ground-Effects kit from Razzi, Part #007-100
The Razzi ground-effects kit is similar to the Erebuni kit above, but is a little more subtle. It also is only for 1988-1990 Grand Prix 2-doors without factory ground-effects.
Razzi, Part #007-100

Rear Wings
The following rear wings are custom designed for the Grand Prix.

This is a wrap-around 3-piece custom rear wing designed to fit on 1988-1996 Pontiac Grand Prixs. I believe it should work on both 2- and 4-door GP's as I believe the trunklids are the same. This rear wing is manufactured by A&A Specialties.
Erebuni Corporation, Part No. 546

This is the factory-style rear wing by Wings West, designed for the 1992-1996 Grand Prix, but since the trunklid hasn't changed, I believe it will also fit fine on 1988-1991 GP's also. This great-looking rear wing is available with or without a 15.5" LED brake light. This is actually better looking than the actual factory wing, because the factory wing uses a regular under-hanging brake light.
Wings West, Part No. 591219 (no light), 591219L (with 15.5" 60-LED light)
Erebuni Corporation, Part No. 513RW (no light), 513RWL (with 15.5" 60-LED light)

This is a BMW M3-style wing for the Grand Prix it is designed for the 1992-1996 Grand Prix, but since the trunklid hasn't changed, I believe it will also fit fine on 1988-1991 GP's also. It is available with or without an LED brake light.
Erebuni Corporation, Part No. 172RW (no light), 172RWL (with 15.5" 60-LED light)

Universal Wings
If you don't care for any of the above rear wings, you may want to choose a Universal one.