Exhaust Systems:
* Affordable Options (Focus on Sound): Flowmaster, Magnaflow, and even some generic brands offer budget-friendly exhaust systems. These will usually offer a more aggressive sound than the stock system. Expect a modest performance gain, if any. Look for systems that specify compatibility with your engine size.
* Performance-Oriented Options (Focus on Flow): Companies like Banks Power, Gibson, and even some custom exhaust shops can provide systems designed for improved flow. These often feature mandrel-bent tubing for reduced restriction and may include headers (more on that below). These will generally be more expensive than basic systems and might yield a noticeable performance increase along with a more pronounced sound.
* Considerations: When choosing an exhaust system, pay attention to:
* Material: Stainless steel is more durable and corrosion-resistant than aluminized steel.
* Pipe Diameter: Larger diameter piping generally allows for better exhaust flow (but too large can be detrimental).
* Muffler Type: Different muffler designs produce different sounds and levels of performance. Research the sound clips available online.
Engine Parts (Air Intake & More):
* Air Filters:
* K&N: A popular choice known for its washable and reusable design, offering potentially improved airflow and performance. Ensure you select the correct filter for your engine.
* AEM: Another reputable brand offering high-performance air filters.
* Stock Replacement: A good quality paper filter from a reputable brand (like Wix or Napa) is a cost-effective option that ensures proper filtration.
* Headers:
* Headers replace the stock exhaust manifolds and significantly improve exhaust flow. They're generally considered a more significant performance upgrade than just an exhaust system alone. They can however increase engine noise and may require tuning adjustments (or may not be legal in your area). Finding ones specifically for a '91 YJ might require some searching.
* Other Performance Parts:
* Intake Manifold: Upgrading your intake manifold can improve airflow into the engine, but this is a more involved modification.
* Throttle Body: A larger throttle body might be helpful in conjunction with other modifications, but it's not always a worthwhile standalone upgrade.
* Ignition System Upgrades: Upgrading the ignition system (e.g., with a performance distributor or coil) can also contribute to performance gains.
Important Notes:
* Legality: Check your local regulations regarding exhaust noise levels. Some modifications might not be street legal.
* Engine Size: Always verify compatibility with your specific engine (4.2L or 2.5L).
* Installation: Installing some of these parts, especially exhaust systems and headers, may require mechanical skills or professional installation.
* Tuning: Significant performance upgrades might require tuning (e.g., adjusting the carburetor or fuel injection) to optimize engine performance and prevent damage.
Before purchasing any parts, it's highly recommended to research reviews, check for compatibility with your Jeep's engine, and consider your budget and performance goals. Forums dedicated to Jeep YJs (like JeepForum.com) can be invaluable resources for finding recommendations and advice from other owners.
