Joined: Nov 2016
Given the level of control that modern computers have over your engine's operation, yes. It affects much more than spark. It also adjusts the cam timing, and injector pulse width as well. These three critical aspects of your engine's operation have a significant effect on how it's going to perform, as well as mileage, reliability, and octane sensitivity.
Most engine tunes don't affect you in a beneficial way, unless you have modified the engine. Once you put on some different heads, cams, intake, exhaust - these changes ensure that the factory tune is no longer optimal. Without taking the time to adjust things, your air/fuel ratios and timing can hurt not only performance, but even risk engine damage if the timing of events isn't well-matched.
A lot of people throw an 'aftermarket tune' on a stock engine and brag about how much harder the 'top end pulls', when in reality, a lot of them actually hurt the low to mid RPM power, and just give the illusion of more power at higher RPMs when it starts to perform more normally.