Guardiola left City's joint all-time leading goal-scorer Sergio Aguero on the bench but his side still struck twice in a frantic five minutes at the Hawthorns which featured three goals in all.
Leroy Sane's stunning strike gave City a 10th-minute lead only for Jay Rodriguez to equalise soon afterwards.
Guardiola believes City have found their killer instinct
But come the 15th minute, City were 2-1 up after Fernandinho let fly with a speculative shot that deflected off Gareth Barry and went in off the post.
City substitute Raheem Sterling gave the visitors a two-goal lead in the 64th minute only for the Baggies' to pull a goal back late on through Matt Phillips after a defensive blunder by Nicolas Otamendi.
"You cannot win all the time by four, five, six goals, that is unrealistic," said Guardiola, whose side have won 28 points from a possible 30 in their opening 10 league games this season. "It's important when you make a good performance you win comfortably and when you don't play at the high level you're able to win."
Stones hails Guardiola for resurgence
Second-placed Manchester United and Tottenham Hotspur started the day level on points but Jose Mourinho's men edged ahead after substitute Anthony Martial's goal nine minutes from time gave them a 1-0 win over a Spurs side missing injured England striker Harry Kane.
"Today, every ball looked like the last ball of their careers," said United manager Mourinho, who slammed his players' attitude following a shock 2-1 loss to Huddersfield last week.
This was Spurs' second defeat of the week after their League Cup loss to London rivals West Ham.
Guardiola 'satisfied' after Chelsea win
"It was our mistake," said Spurs boss Mauricio Pochettino after his defence failed to deal with a long clearance from United goalkeeper David De Gea that Romelu Lukaku headed on to Martial.
Meanwhile, Arsenal moved to within a point of north London rivals Spurs after coming from behind to see off struggling Swansea 2-1.
Reigning champions Chelsea in turn went level on points with Arsenal after Eden Hazard's 51st-minute goal proved decisive in a 1-0 win away to Bournemouth in Saturday's late kick-off.
The Blues are now nine points off the summit and Hazard, asked if Chelsea could catch City, replied: "The season is long, you never know what can happen."
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