FCB go into Saturday's clash having scored nine goals and only conceded one in their first two fixtures of the season. They put six past Stuttgart in their last match with Thomas Muller grabbing a double.
And Heynckes says it shows they have the desire and hunger for more.
“It shows the team is hungry and has rediscovered its appetite," the 67-year-old told the official club website.“We have to prepare very thoroughly, because it'll be a hard job. They are very difficult opponents."
The Bavarian giants look set to give new €40 million midfielder Javi Martinez his debut but Heynckes knows they cannot underestimate the visitors as FCB suffered a shock 3-2 defeat to Mainz last season.
He added: “We have to be just as aggressive as we were against Stuttgart, accept the rules of engagement laid down by our opponents, and exploit our footballing class in attack."
Bayern are without the services of Mario Gomez, David Alaba and Diego Contento through injury. While there is still concern over Toni Kross fitness with a groin injury, Arjen Robben is now fit again after missing international duty with the Netherlands in midweek.