The same problems that all " one size fits all " tuners are known for. The biggest of which is smoking the tranny because your tuners DO NOT reprogram for the new power band. Also, head gasket failure. Although any tuner will blow head gaskets if put on the highest power level and run like a dragster without studs, the non-custom tunable tuners are much worse about this. Its mostly due to the fact that there are hundreds of different strategies on these trucks and each one runs different. Your tuners make minimal changes to make a little more power without taking into consideration any specifics of each vehicle. With the SCT or Edge Gryphon, you actually talk to someone and explain what you have modded (Studs, EGR delete, Turbo, Injectors, Intake, etc.) and he/she will build a tune/s made specifically for your vehicle and strategy. The transmission is also adjusted in these tunes to account for the dramatic change in power. The SCT and Gryphon units also rewrite your computer while saving a copy of your stock file so you can go back to a stock setting without leaving a trace of the tuner. Oh and here are a few other things to take into account; tire size, gear changes, more smoke, less smoke, shift firmness, line pressure, boost, cylinder pressure, torque converter settings, WOT shift points, engine braking, along with countless other parameters can be adjusted by a tune writer of the customers choice to achieve the absolute perfect driving experience. Not to mention the incredible power gains achieved by custom tuners while still being able to keep a specific engine as safe as possible. Once again, this is accomplished by knowing the customer, the customers driving habits, the customers vehicle, and its list of mods. You sell a product in a box and never know anything about the person purchasing or the vehicle it will be used on. These tune writers make a living and support their families by make good, safe tunes for individuals and their vehicles. If they build crappy running or unsafe tunes customers will go elsewhere, so they take the time to ask questions and get it right so their reputation stays intact. "One size fits all" tuners will never hold a candle to custom tuners or the custom tune writers that program them and that is a fact.