Can you explain the differences in the way it works vs the TST I have in laymans terms please?
Very similar... both advance injection timing (squirt fuel into the cylinder sooner than stock) and extend injector pulse width (leave the injector open longer so it dumps more fuel into the cylinder). The way they hook up is slightly different. Both connect in-line with the injectors and MAP sensor. TST has in-line connectors for the cam and crank sensors. The Juice has a single data link connector, and alters timing by talking directly to the ECM.
Both have EGT-based de-fueling (allowing you to set a maximum EGT, and the box will try it's best not to let EGT's go over that mark). The Juice also has boost-based defueling, meaning that it will try and keep the turbo below a specified boost level (good for keeping the stock turbo in one piece).
TST gives you 9 power levels (from about 30HP up to about 150HP), and 9 torque enhancement settings (low-RPM fueling), as well as stock settings (box completely off). The Juice gives you 5 power levels (from about 25HP up to about 100HP) and 5 low-boost fueling settings (similar to TST's torque enhancement) - no provisions for completely disabling the box, however.
The TST display shows EGT and boost. The Juice w/ Attitude has a configurable LCD display that can show many parameters (EGT, boost, speed, intake and engine temp, etc). The Attitude can also measure 0-60 and 1/4-mile performance.
For automatics, the Attitude has some transmission slip detection capabilities, and can de-fuel when slippage is detected.
TST plusses: more power, more adjustability, available for '03/'04
Juice plusses: Better display, slightly easier install, friendlier to stock vehicles
-Tom