The result left Pep Guardiola's men one win away from completing a much sought-after treble as the Premier League victors will face Inter Milan in next weekend's Champions League final.
Gundogan, whose brace included the fastest goal ever scored in FA Cup final history when he netted after just 12 seconds, was non-committal when asked about his future.
"To be honest, I don't need these kind of days to feel appreciated and to feel special in this club," he told the BBC.
"I know that, that's why I am already here seven years with all the up and downs that I've had so far, and nothing is decided yet. So we're going to see what's going to happen."
![Gundogan was the star man for City Gundogan was the star man for City](https://livesport-ott-images.ssl.cdn.cra.cz/r900xfq60/e7b9b700-b801-42bf-9399-8daccb0f194f.jpg)
Guardiola had no answers either, saying he was "hopeful" his team can re-sign the German international who has been linked to several other clubs including AC Milan and Arsenal.
Fans had barely settled down in their seats when a beautiful long volley from Gundogan ended up at the back of the net.
"The ball just was placed amazingly for me and I just had to hit it," he said. "Obviously it was quite a good strike and it went in and it was amazing."
He scuffed a second volley past United keeper David De Gea to seal the victory for City.
Gundogan has been an unsung hero for City behind goal-scoring machine Erling Haaland, who has scored 52 goals in all competitions in his debut season for the club.
The German nearly netted a hat-trick on Saturday at a sun-soaked Wembley Stadium, but what would have been his third goal was flagged as offside.
![Gundogan raises the trophy with his team Gundogan raises the trophy with his team](https://livesport-ott-images.ssl.cdn.cra.cz/r900xfq60/6b5b6708-1dad-45b1-b413-22c77b454d96.jpg)
With City aiming to become only the second English club to complete the treble, and emulate Manchester United's 1999 feat, Gundogan's focus quickly switched to the showdown in Istanbul against Inter.
"Obviously we are playing finals to win them and especially that one will feel even more special," Gundogan said.
"Getting to the final for the second time in three years, it's already a great achievement, and I feel that now we have to do it. And this is the target for next week."