Its true to some extent. I don't think you should expect wild gains in power or anything else. In my experience the biggest noticeable differences with an ECU memory reset are idle speed/quality and shift points for ECU controlled auto transmissions. Then I'm not the most observant guy in the world, either...
I would like to know how the "steering will get very light". There are plausible explanations but most cars' ECUs don't have control over P/S operation. Fiat could have an electric rack motor or hydraulic assist modification capability, though.
Toyota MDT in MO