Here are just SOME of the extensive changes we made to the GXP ECM/TCM in the name of more power, reliability and drivability: • Proprietary extensive fuel and spark mapping. • Remove top speed limiter • Firmer part and full throttle shifts. • Revised up and down shift points to take advantage of the engines RPM band and newfound power; no more having to tap shift in the quarter or short shifting in drive. • Proprietary torque management adjustment - there is still important torque management in the transmission calibration. • End users have reported an increase in fuel economy (Your mileage may vary)
Most users report a gain of around two miles per gallon when using 91 or 93 octane fuel as well as 15-20+ wheel horserpower on the dyno! This is one of the easist mods you can make to your LS4 equipped W-body that also yields the most performance per dollar.
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Customer Reviews:
Michael Parent (Friday, 12 March 2010) Rating: Great tune, easy to deal with. Great customer service. I liked this tune so much I ordered their VMX PowerCal Cable. Can't wait to try that out too.
Grand Prix 
