The N10 dual exhaust y-pipe was available on '89-and-later cars, and is reputed to be worth 10 hp. This is a New Old Stock unit, and includes the AIR pipe for the cats. It requires the later high-flow exhaust manifolds and a dual-cat specific after-cat system, so it's not simply a bolt-on upgrade.
Although the tires and shocks will be of little use after 20 years of service, the front and rear sway bars will make substantial improvements in handling, even with otherwise stock Firebird springs. They're also an easy bolt-on, with the correct bushings and end links. With the addition of high-quality shocks, struts and tires, installing the WS6 suspension package will result in an excellent handling budget-based Third-Gen Firebird.
Though further improvements can be made via additional chassis reinforcement, such as subframe connectors and strut tower braces, these were never made by the factory. However, a suspension component that is unique to the Chevrolet IROC-Z-but is also effective on Firebirds-is the steering brace or "Wonder Bar."
It's mounted between the front subframe horns and the front sway bar mounts (see photo). The Wonder Bar improves steering manners and prevents cracks in the subframe at the steering box mounts. The stock Chevrolet part is flimsy and most that we've seen in the junkyard are bent, so consider spending $50-$60 on a sturdier aftermarket version from Top Down Solutions, Hawks or BMR Fabrication.
Another simple upgrade is to swap in urethane sway-bar end-link bushings, found on Third- and Fourth-Gen performance package cars. They are only about $15 a side new, with upgraded hardware from Top Down Solutions, so don't sacrifice any limbs to get them at the junkyard.
GTAs or 1LE cars often come with aluminum driveshafts, which are reported to be worth a few horsepower as they require less energy to spin, and are easy to remove and install.
These seats from a Sunfire needed to be cleaned, but fit when bolted onto the Third-Gen seat mounts. Other seat donors include Sunbirds, Fieros, and Fourth-Gen F-bodies. To clean stains, rent a carpet steam cleaner with an upholstery tool at your supermarket, then spray 3M Scotchguard on the seats after they dry.
Fuelish Upgrades
Many Third-Gen F-bodies suffer from cracks in the fuel tank filler necks because of their unsupported design. This can cause a gas odor and fuel leakage down the outside of the tank and left-rear quarter-panel. Another common issue is fuel starvation on right turns when cornering hard. If you decide to replace your fuel tank, source one from a '90 or later, as all those F-bodies have baffles in the tanks to reduce the fuel starvation. The '90-and-later tanks still have the filler neck cracking problem, so make sure it's properly sealed and supported before installation.
Any WS6 (16x8-inch) wheels are popular junkyard quarry, but beware, as many 16-inch Trans Am/Formula "Hi Tech" wheels look the same at first glance. However, different years have different dishes, cap designs and rim lip treatments, so mismatches are common. All 16x8 wheels for Third-Gens were built with different offsets for front (zero offset) and rear (16mm positive offset), so try to find a complete set off the same car in the yard, or purchase a matched set from Hawks Third Gen. The 16-inch IROC wheels can also be used and have this same offset, but are a very different style than the Pontiac wheels. Using Chevrolet-specific parts could result in a credibility loss for your Pontiac.
Go Big Or Go Home
If you're planning a performance engine build, a great junkyard score is a 5.7L (350) block, as it is exactly the same price to rebuild as a 5.0L (305) and has substantially more performance potential. The 350s are available in automatic transmission-equipped Third-Gens from '87 on. Although external dimensions are identical to earlier Chevy V-8s, all F-body V-8s changed in 1987 to include center-bolt valve covers, a hydraulic roller cam, a single-piece rear main seal crank, a different pattern flywheel and a revised intake manifold/cylinder head bolt pattern, so few internal parts interchange with the '86-and-earlier engines.