Royal Purple
Fluids are important to maintain a top running motor. The only non-Honda fluid that should touch a Legend is quality synthetic engine oil. Honda's oil is great, and everyone has their preference, but I use Royal Purple. Additionally, it's wise to drain and fill all fluids, especially the transmission, frequently.
Bayou ECU
The Bayou ECU was originally developed by Dinan (the popular BMW aftermarket company), and later bought by Bayou Performance. Overall, it's a great chip to boost performance. Most people dyno an additional 9whp/9ft.lbs (coupled with an intake and exhaust). It works by increasing the redline to 7,100rpm for the Type II, optimizing the air/fuel ratio and slightly raising shift points on the automatic.
G2Legend Performance Cold Air Intake
Placed into limited production after man-weeks of custom development, this intake is arguably the best ever offered for a Legend, and quite easily my favorite performance mod. The dyno results show a 20whp gain around 2.5k--impressive. Mine was specially ceramic coated to keep the metal cooler. If pure performance wasn't enough, the intake rumbles a throaty growl, enough to keep the most particular ears submersed in sound-heaven. Cold air intakes make for an excellent first performance modification.
Throttle Body Coolant Bypass
Moreover, keeping the intake cooler results in less loss of power from an expanding air vortex due to the otherwise scalding hot throttle body. The throttle body coolant bypass made a noticeable difference as the 'leg doesn't bog down so much in dry heat of California's summer. This modification is relatively simple if you feel comfortable with the Legend's engine bay. Click the link for instructions.
EGR Block Plate
Installing the custom EGR block plate prevents exhaust gasses from entering the intake manifold. The benefit is a slight power gain at midrange throttle, as that's when the Legend's EGR system kicks on.
6-Wire Grounding Kit
Grounding kits should be considered a general maintenance item. My experience saw easier starts and smoother idling. Audiophiles enjoy noise reduction in their sound equipment from the better grounded electrical system. The above link provides an excellent install.
Spoon Reservoir Tank Covers
Spoon reservoir tank covers not only dress the engine nicely, but serve to catch any brake fluid over-spill and prevent possible fire hazards.
2.5" cat-back Piping
Less restrictive air flow results in net gains of power. 2.5 inches seems nearly perfect diameterwise for the naturally aspirated 3.2l Legend's cat-back. I noticed an accompanying raise in exhaust volume.
Remus 2.5" Turbo II Muffler
Argueably the best muffler, Remus loved the Legend so much that they designed a custom muffler for it; who can blame them? I bought their Turbo II universal fit muffler for the apperance that I wanted (pictured). Of course, their most popular model is the Legend specific.
Custom Aluminum Pulley Set
These custom pulleys combined weigh 52.3oz versus 116.45oz of the factory pulleys (a 55% weight reduction). The average peak gain was 10whp and 10ft./lbs. of torque. I noticed an obvious increase in throttle response. Click here for a movie of the pulleys in action.
Planned
Apexi S-AFC II
Mangnaflow 2.5" High Flow Cat
Stromung Headers
SMS 2.5" Stainless Steel Y-Pipe
Stromung 2.5" B-Pipe