Besides Upsolute, some of you may wish to consider the RennTech ECU Performance Upgrade. It is more expensive but the original Mercedes chip in the Crossfire is overwritten, not replaced. The Renntech technician in the L. A. area was in computer contact with a technician at the MB factory in Germany during the upgrade on my Crossfire Roadster. Both used the actual MB software program that originally wrote on the ECU. The top speed limiter is also raised from 158 MPH to over 186 MPH. You can visit the Renntech website to see the various improvements they make in HP, Lbs.-Ft. Torque, etc. I especially like the smoother gear shifting it creates if you have an automatic transmission (100 RPM increase in first and second gears).
Renntech headquarters in Florida told me that you are not going to get an increase above 15 - 20 HP in a Standard or Limited Crossfire (NOT SRT-6) no matter what company's chip you use because MB sets the specs closer to the maximums now during production. They also told me that there are no detectable changes in smog control testing. The dealership will not notice any change so it doesn't affect any warranty. The only way to test for ECU modification is with a dynamometer.