A tune is always recommended with added mods on these cars.
Meth is a fuel, so if you install it and drive it w/o a tune you will be running rich on WOT. If your too rich, you'll get bore wash & murder your motor slowly.
The tune is needed to adjust your fuel trims to make it a tad leaner (since you can w/ meth) & increase boost to make more power. It burns hotter thus, creating mad torque & spool.
A tune tells the ecu how to compensate for the meth & make it work with your car, not against it.