From the website:
"The Pro mod is designed to improve clarity and lower the noise issues that the stock GE-7's have. This is accomplished by upgrading the IC chips and tone capacitors. We replace the cheap stock tone capacitors with high quality film capacitors like we use in the rest of our effects. This improves the overall clarity of the pedal.
VOLTAGE : The stock GE-7 can not be run over 15V. We modify it so it will run
fine from 9V up to 18V. Higher voltage which will give even more clarity and headroom to the pedal.
The stock GE-7 can add some noise if you move the sliders away from center. Even bringing the two lowest sliders DOWN will add noise, try it! Our mod replaces three chips with the King of Tone chip, which is a low noise chip designed for tone controls so it's perfect in this application. These chips take about 40% more power (pedal goes from 16mA to 23mA), so a battery will not
last as long, better to use a power supply. A normal alkaline battery will still last over 15 hours, so you can use batteries if you want.
We also change a bunch of cheap capacitors used for tone control to high grade metal film caps. This lowers noise and improves tone."