A mail order tune like trifecta or vtuner can give you just as much power as a dyno done tune.Its all depends if the tuner is willing to data log you several times and tweak the base tune.The GM Torque PDI will calculate flywheel HP and TQ output.This can be used to tweak to max safe output.Also you will make more power if tuned for 93 octane than 91.
A mail order tune will not give you as much as in person dyno tune followed by a street tune.. That has been proven not only on Mpfabs car but also mine and on another member and also others outside the sonic/cruze world. I myself made 20 more TQ before going back to a canned tune. This summer I'm going back to using HPT for drivability and power.
Unless you can prove me wrong on that an actual in person tune wiill be better And for 300 to 400 it isn't a to expensive
There's a lot of variables involved when tuning. Ambient temp, altitude, fuel delivery, etc with that a custom tune will always give u more power and Better drivability.
What's so fun about making the same amount of power as every tuned cruze or sonic