* Dynamometer: Dynojet, Courtesy Of Hybridynamics
* Testing & Installation: Hybridynamics
Pros
Its V-8 engine. Let's face it; there really is no replacement for displacement. Technology honed by Japanese automakers has come a long way in increasing the efficiency and capabilities of smaller engines, but the same technology applied to a bigger starting platform will always yield more power. Toyota's 1UZFE engine offers 4.0 liters, eight cylinders and 10.5:1 compression for torque, but with four valves per cylinder, quad cams and VVT-I for efficiency and power across its entire rev range-the best of both worlds.
Cons
Its V-8 engine. Power and torque advancements aside, V-8s are large, heavy, bad on gas, and cursed with the stigma of being somehow related to American Iron. As such, there are few performance upgrades available for it, and the bulky GS400 platform that it lugs around.
Notes
If the dyno runs generated by our GS400 look a little flatter than usual, that's happening for two reasons. The first being that V-8 engines simply make loads of low-end torque-with such a short redline, ours made more of it that horsepower up top. The second is that testing the GS began at 3,750 rpm at each stage, as this was the lowest engine speed its automatic transmission would lock into gear.
Pros
As with many older, big-displacement platforms, power and torque increased across the board by replacing the restrictive factory intake system with a free-flowing K&N unit. USA-made construction, washable filtration and million-mile warranty mean you'll enjoy these benefits for years to come. CARB exemption lets you do it without hassle from the law.
Cons
None.
Parts
Intake filter, tube and heat shield; silicone couplers; MAFS mounting hardware; vacuum hoses; CARB exemption
Tools
10mm socket, ratchet and extension, flat- and Phillips-head screwdrivers, pliers
Installation Time
45 minutes
Notes
Characteristic of big-displacement V-8 engines, low-end power and torque production jumped significantly, and nearly 15 whp was seen in the low rpms, and even more torque-welcome additions for highway driving.
Pros
Mandrel-bent, TIG-welded Japanese construction; mature, high-quality appearance and sound; and performance gains where they count.
Cons
Size. The A'PEXi exhaust is a dual, cat-back unit, with mufflers that come welded to lengthy rear sections of piping. The unit ships in two very large boxes, so expect high shipping charges, and plan to pick it up in a vehicle larger than a Miata (the mistake we made).
Parts
Dual mufflers with attached rear section piping, intermediate pipe, gaskets and hardware
Tools
14mm wrench, socket, ratchet and extension, hanger tool, PB Blaster
Installation Time
1 Hour
Notes
As we thought it would, freeing up the exhaust flow of our GS's 1UZFE decreased low-end power and torque a bit. There's simply no way around this; making power up top (notice the linear power increase after 4K rpm) requires reducing backpressure, which decreases torque. An added benefit, the A'PEXi unit made our GS look and sound downright gangster... a big plus.
Pros
Mandrel-bent and TIG-welded stainless steel construction, small-batch reliability, simple installation, and power and torque gains throughout.
Cons
P.I.A. installation on older cars, particularly those from snowy, northern climates (like ours) on which every single nut and bolt is corroded to the point of non-existence. Angle grinders and patience work great here.
Parts
Y-pipe, gaskets, hardware.
Tools
14mm wrench, socket, ratchet and extension, angle grinder (if rusted)
Installation Time
1 hour (if rusted)