The system incorporates the OE throttle body, though this is ultimately up to user. Magnuson reports that an aftermarket 90mm unit is good for another 40hp.
Fuel system upgrades include a fuel pressure regulator adaptor with a higher discharge rate.
Since the Radix is designed for a totally stock engine, it draws incoming air from the stock air box and plumbing but includes a K&N element. We’d already installed a K&N FIPK cold air intake, so we adapted the Magnaflow trunk to the K&N fixture and made it look factory sweet.
Throttle response is immediate and potentially devastating. If you’re not careful with the loud pedal, you’ll blow the tires off. The overall impression is one of a powerful forward surge forward and at the upshift of every gear the 5,000-pound dog literally leaps ahead. On the practical side (yes, there is one) during normal driving, less throttle input is required to get the same results simply because low-end torque has it all by the throat.
At the clandestine dragstrip the results were not so positive. Regardless of launch technique, torque compromised the 285/50ZR18 Bridgestone Dueler H/P Sports and the best we could muster was a wheel-spinning 14-flat at 105. No bite, no glory. Call it a skanky cop-out if you like but building a throttle-flogger wasn’t the goal, not at all what the project was about. We wanted reliable, instantaneous reaction in the real world. Without losing a shred of practicality or function and with at least 450 horsepower and 440 lb-ft of torque at the wheels, how much more juice does this driver really need? With the price of a petrol nearly twice what it was at the onset of this program, our big dog gets to snooze in the garage most of the time.