Both were outstanding in City’s 3-1 win over Arsenal in midweek.
De Bruyne scored a superb opener and made an assist for Erling Haaland, while Grealish also scored against the Gunners while being a constant threat throughout.
But the boss believes there is even more to come from both players in the coming weeks and months.
“Obviously Jack is playing really good,” said Pep.
“I’m not talking about decision making, we talk about his ambition or aggression.
“Attacking the backline, the quality was always there, but his commitment to take a risk and important decisions right now makes the difference.
“He has to continue (doing this).
“Kevin is playing really good, too. It’s like Jack, I’m so pleased for everyone, but I want more.
“I had the feeling Kevin can do more, and Jack can do more.
“They can do better. They can do it. Kevin made a fantastic goal, I know the demanding schedule we have in front of us until the end of the season.
“We have tough, aggressive opponents (to play).
“We need the players who have the feeling we can do better.”
And Guardiola provided encouraging news on England defender John Stones – though he isn’t available just yet.
When asked how close he was to a return, Pep said: “He’s getting better. When (will he return)? Tomorrow? No.”
