I'm no Pac-Man expert and I don't use any patterns, but I always got the impression that the "pros" are quite satisfied with the timing in MAME.
One thing to consider is that there are two ways to turn a corner in Pac-Man. You can do a simple turn, or you can "cut the corner" by pressing the joystick in the desired direction and holding there, before reaching the intersection. The latter method gives you a slight bump in speed if, for example, Blinky is on your ass.
If you accidentally mix and match these two types of turning, I think it might throw off the overall timing just enough to break some patterns.