Not necessarily. Let me rephrase my example. Let's say you start with an engine that produces 150 hp stock. Tuning the engine management will net a 15 hp increase to 165. This is indeed a 10% increase. Now, take the same engine with a stage 1 turbocharger kit, assuming it already has a reasonably high compression ratio, but run stock the stock ecu map. You can probably get away producing 250 hp without blowing up the motor. Now, add proper engine management and the output increases to 300 hp. That's a 20% increase, which is double what the N/A's gains are. This is due to advanced boost control, enrichening the a/f mixture to allow more boost, etc. I think it would be great if the user have control over the aggressiveness of the tune to try to adjust the driveability so you can produce either a less powerful but more useable flat torque band (good for auto-x and touge), or a laggier, but peakier power curve (good for drag and ovals).