It has nothing to do with his system. Maybe your perception is too slow to notice the lag? I've tried this over the past few years with three different computers. ALL of them had input lag. I've tried it with wired and wireless keyboards as well as a wired xbox controller (well, a 3rd party madcatz one). This latest one is with a wireless steam controller. There has always been a very slight delay from the point I hit the button or key to when the flipper flips.
Rather than suggest it's his system, maybe a simple google search would reveal that this has been a well known problem for years with this game.
Other than the lag, it's a decent pinball game. Decent graphics and sound. Table design and rules are a little weak for some of them but it's still fun.
Also worth mentioning is that the lag is common for several of the popular pinball games. It's not limited to FX2. It's just that pinball and fighting games (which I personally don't like) are two of the most sensitive to input lag.