Plexus IS300 1st‑Gen SE Body Kit Guide: Fit, Style & Cost

If you’ve ever admired the sleek silhouette of a Nissan GT‑R and wondered how to give your own IS300 a comparable edge, you’re not alone. The Plexus IS300 1st‑Gen SE body kit promises exactly that – a blend of aggressive aerodynamics and subtle Japanese‑inspired flair. In this guide we’ll walk through what the kit includes, how it fits on the first‑generation SE, material choices, typical installation steps, price ranges, and a few practical tips to keep the look sharp for years to come.

What’s Inside the Plexus SE Kit?

The Plexer (yes, Plexus) kit for the 1999‑2005 IS300 SE is a bolt‑on package that covers the most visible exterior panels. Typically you’ll receive:

• Front bumper with integrated splitter and dual‑air intakes.
• Rear diffuser and optional wing (some versions ship the wing separately).
• Side skirts that blend into the rocker panels without requiring major cutting.
• Rear bumper featuring a subtle lip and enlarged exhaust cut‑outs.
• Optional hood scoop and roof spoiler for enthusiasts who want extra visual punch.

All pieces are designed to match the stock mounting points of the first‑generation SE, meaning you won’t need to drill new holes or modify the chassis – a key selling point for DIYers.

Materials: Fiberglass vs. Polyurethane

Most Plexus kits come in two material options, each with its own set of pros and cons.

Fiberglass

Fiberglass is the classic choice for body‑work. It’s lightweight, relatively inexpensive, and can be sanded to a smooth finish before painting. However, it’s also more prone to cracking if you hit a curb hard or expose the kit to extreme temperature swings.

Polyurethane

Polyurethane offers superior flexibility and impact resistance, making it a better fit for drivers who regularly navigate rough roads. The trade‑off is a slightly higher price tag and a finish that can be a bit more challenging to prime and paint evenly.

When deciding, consider your driving habits, budget, and how much time you’re willing to spend on preparation before the final paint job.

Fitment Specifics for the 1st‑Gen SE

The first‑generation IS300 SE differs from the standard sedan mainly in its rear spoiler and slightly altered rear bumper geometry. Plexus engineered the kit to accommodate these nuances. The front bumper aligns with the stock mounting brackets, while the side skirts are tapered to clear the SE’s wider rear track. The rear diffuser slots into the factory‑mounted diffuser recess, preserving the car’s original exhaust layout.

Because the kit is a direct bolt‑on, you’ll typically need only a socket set, a few trim removal tools, and possibly a drill for the optional wing brackets (if you choose the wing). No welding or custom fabrication is required for a proper fit.

Installation Overview (DIY Friendly)

While a professional installer can finish the job in a day, many owners report a smooth weekend project. Here’s a condensed step‑by‑step rundown:

1. Remove the factory front and rear bumpers, along with any trim pieces that interfere with the new components.
2. Test‑fit each Plexus part to confirm alignment; make any minor adjustments before committing to bolts.
3. Attach the front bumper using the original mounting points, then secure the splitter and intakes.
4. Install side skirts, ensuring they sit flush against the rocker panels.
5. Mount the rear diffuser and, if included, the wing or spoiler, following the kit’s hardware guide.
6. Re‑install any removed trim, then double‑check for gaps or misalignments.
7. Finally, prep the surfaces for paint – a light sanding, primer coat, and then your color of choice.

Most users recommend a final torque check after the first 48 hours of driving, as the bolts can settle once the kit warms up.

Cost Breakdown

Pricing can vary based on material, retailer, and whether you purchase a complete set or individual pieces. As of 2024, typical ranges are:

• Fiberglass full kit: $1,200 – $1,500 (excluding paint and labor).
• Polyurethane full kit: $1,600 – $2,000.
• Optional accessories (hood scoop, wing): $150 – $300 each.
• Installation labor: $300 – $600 at a reputable body shop.

When budgeting, also factor in the cost of a high‑quality paint match, which can run $200–$400 if you’re having the kit painted to blend with your factory color.

Styling Tips to Maximize the Look

The Plexus kit is designed to complement the IS300’s natural lines, but a few styling choices can elevate the effect.

• Matching paint finish: If your car is a matte or satin shade, consider a matching matte clear coat on the kit to avoid a glossy “patchwork” appearance.
• Wheel upgrades: Pair the kit with 18‑inch forged wheels in a dark gunmetal or brushed finish for a cohesive performance vibe.
• Lowering springs or coil‑overs: A modest drop (½‑inch) accentuates the diffuser’s angles without compromising ride comfort.
• Accent lighting: Subtle LED strips under the splitter can add a night‑time presence without looking gimmicky.

Common Issues & Maintenance

Even the best‑designed kits can encounter hiccups over time. Owners frequently report two main concerns:

1. Water pooling behind the front splitter: Ensure the splitter’s drainage holes are clear and consider adding silicone sealant around the lower edge.
2. Minor flex in polyurethane side skirts: This is normal, but excessive flex may indicate loose mounting bolts – tighten after the first 100 miles.

Regular cleaning with a pH‑balanced car shampoo will keep the finish bright and prevent brake dust from etching the material.

Where to Buy

Official Plexus distributors in North America include:

• Plexus Auto – offers both fiberglass and polyurethane options, often with a “paint‑in‑house” package.
• CARiD – stocks the kit in a kit‑only format, allowing you to source paint elsewhere.
• Specialty Nissan forums (e.g., ClubNissan) – members sometimes sell lightly used kits at a discount.

When purchasing online, verify that the kit lists “1st‑Gen SE” compatibility to avoid receiving a version meant for the later 2006‑2008 models.

Frequently Asked Questions

Will the Plexus kit affect my vehicle’s warranty?

Because the kit is a bolt‑on that doesn’t alter factory structural components, most manufacturers view it as a cosmetic modification. However, any damage caused by the kit (e.g., a cracked bumper in an accident) would not be covered under the original warranty.

Can I keep the factory bumper and add the Plexus parts?

Yes, the front splitter and rear diffuser are designed to attach to the existing bumpers, allowing a “partial” look if you prefer to retain the stock bumper shape.

Is it legal to install the kit on a street‑registered IS300?

In most U.S. states, the kit is street‑legal as long as it doesn’t obstruct lights or exceed width limits. Check local regulations, especially if you add a wing that extends beyond the original body width.

How much weight does the kit add?

Fiberglass components typically add about 25–30 lbs, while polyurethane can be slightly heavier at 35–40 lbs. The increase is modest enough that it won’t noticeably affect fuel economy.