ECU upgrades on non-turbo / non-supercharged cars are really not upgrades at all. The changes often sacrafice low end torque for higher HP, etc. In several mod magazines they tested chips which claimed a 10 or 14 hp increase at certain RPMs. While their claims were true the hp/torque curve of the performance chip compared to the OEM chip showed times when the OEM chip had 10 or 14hp more than the performance chip. They did 0-60 testing and showed that out of 10 performance chips made for the V8 mustang 6 actually INCREASED! 0-60 times and actually only one was able to knock 1/10th of a second off 0-60.

In turn they showed adding low restriction air filters and cold air intakes would consistently increase HP with one of the largest increases from low restriction exhaust.