The Hammers took the lead against the run of play in the first-half through James Ward-Prowse after Doku was dispossessed, but the Belgian levelled within 60 seconds of the restart to ignite a stunning City comeback.
Doku, who was named Player of the Match after an electric display, was overjoyed after his first goal for the club.
"It means a lot. A lot. Especially after their goal," he said.
"I wanted to do something back, something good, and I scored and helped the team and I’m happy for that.
"I think we reacted very well. We had a lot of chances in the first-half without scoring but we kept on going. They scored a goal, I had bad touch, so I was disappointed.
"We reacted well and kept on playing and after that we scored three goals and had a good game.
"I enjoyed it [against Vladimir Coufal]. I had a lot of one on ones, the coach knows i’m good at that.
"We go for one on ones. I tried to do it and it worked. I enjoyed the game against him."
The winger made his debut before the international break in our convincing 5-1 victory over Fulham.
The 21-year-old believes that his performance today was only a glimmer of what he has to offer.
"He [Guardiola] said the first game I was a little bit shy, and now I’m not, and I agree.
"I showed a little bit more today of what I’m capable of. I was less shy today.
"I’m not realising yet but I’m enjoying it a lot. It’s a big moment for me and my family.
"Hopefully we can win a lot of games and trophies and I can score a lot of goals."