Mancini took over at Eastlands on 20 December 2009 after City's controversial decision to sack Mark Hughes, with Kidd stepping up from technical development manager to number two the same day.
Mancini failed to lead the Abu Dhabi-owed club into the Champions League last season and came under intense scrutiny after a mixed start this time round.
But the Italian's side are now unbeaten in the Premier League since losing to Wolves on 30 October and have won five of their nine away matches.
Victory at Upton Park puts them alongside leaders Arsenal on 32 points, although their goal difference is five inferior to the Gunners'.
Chasing a first top flight title since 1968, City are one point clear of United, who host Arsenal on Monday, and two above Chelsea, who travel to Tottenham on Sunday.
"We'd like to be in contention come March-April," Kidd added. "If the lads keep working way they are, we should be there. That's what we're aiming for.
"The boss has put a tremendous work ethic in and the work he puts in on the training pitch, tactically and team shape, is superb. He's never off the training pitch and it's a credit we've got him.
Mario is a fantastic talent, he won't be a problem. He's a young lad who has come into a tough league - he's learning every day, gradually growing into it
"I'm privileged to see him work and I'm personally glad now it's coming to fruition for him."
City outclassed West Ham in a ruthless performance that enabled them to maintain their unbeaten record on visits to London under Mancini.
They opened the scoring through Yaya Toure and doubled their advantage when the Ivorian's shot hit the post and went in off the back of Hammers goalkeeper Robert Green.
Substitute Adam Johnson rounded Green to make it 3-0 before James Tomkins headed a late consolation.
"It was very pleasing, a really good performance," Kidd enthused. "The boys worked really hard. We knew it was going to be a tough game but full credit to the lads.
"The boss has worked really hard this week on making them be focused. The effort, the commitment it appears to be getting through now.
"We have class acts but we always look for a team effort. The individuals will come through and win you the game but the big ethic we've got is team work. That is the important thing."
Grant unconcerned by Hammers defeat
While Yaya Toure and fellow midfielder David Silva were particularly impressive, one individual who endured a disappointing afternoon was 20-year-old striker Mario Balotelli.
Italian Balotelli, who joined from Inter Milan for about £24m in August, made little impact against the Hammers and was booked for dissent before Mancini replaced him with Johnson shortly after.
"He's a young lad who has come into a tough league - it's different from Serie A and it will be a little bit of a culture shock to him," Kidd commented.
"He's learning every day of the week, gradually growing into it. Mario is a fantastic talent, he won't be a problem."
West Ham boss Avram Grant had no complaints with the defeat, which keeps his side bottom of the table on 12 points with only two wins all season.
"The boys tried very hard today, it was not easy," said the Israeli, who succeeded Gianfranco Zola in the Upton Park hot-seat in June. "City are a very good team - you just look at the players who are not even on the bench.
"First half we didn't pass the ball very well but second half we were good until they scored the second goal. We were dominating and they scored on the counter-attack."
Grant suggested the Hammers should focus their attentions on beaten teams who are closer to them in the table, with their next three fixtures against Blackburn, Fulham and Everton.
"We tried but these are not the teams we need to compete against, they are better than us," he stated. "I'm very pleased with the spirit of the boys.
"These [the next three games] are the games that are very important to us because when we play against Manchester City we try our best but we know they have quality and are strong physically.
"We play against teams now who are not better than us and we will try to take points. I'm not thinking about my position, I'm thinking only that I need to do my job.
"Our position is not so good and I don't need to think if my job is like this or like that. My job is to improve the team and take points, especially in the next games."
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