Harriers played some scintillating football and scored four times in the second period to beat their in-form visitors.
The victory moved Kiddy up to sixth in the National League North and they are now unbeaten in their last 15 League games.
When asked if the three points put pressure on their play-off rivals, Eustace said: “We’re not interested in anybody else, we just keep doing what we want to do.
“It’s well known that we had to rebuild the group at the start of the season and it took a while to get the players in. The new players had to learn how we want to play and slowly we’re getting there.
“We just want to continue playing some good football, getting the results and seeing where it takes us.”
Skipper Ryan Croasdale and Joe Ironside put Kiddy two ahead after the break before FC United’s Zac Corbett was shown a straight red for an off the ball incident.
Sub George Waring headed home on his debut and then Elton Ngwatala scored a fourth as Harriers enjoyed a comfortable night at Aggborough.
“I thought we were excellent against a very good team,” Eustace added. “They’re a difficult side to play against so it’s a fantastic result.
“We’re doing very well at home but we’re also doing well away. We just haven’t taken our chances at times but we’re unbeaten for a long time away from home.
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