Gundogan, who claimed assists for both of Aguero's goals, credited his teammate's timing and movement for helping City come from behind against Sean Dyche's high-flying side.
"The timing was just perfect," Gundogan told Sky Sports News.
"Sergio passed the ball to me and I just had to save it. I was waiting for the run and Sergio was just at the right time in the right spot. I was quite sure this ball was going through.
"Luckily both actions were a goal and 2-1 was very important at that point. After that, we had all our confidence back, started to keep the ball and play very well. We scored two more and we are very happy with the result."
The draw for the fourth round of the FA Cup takes place on Monday evening.