Try watching closely or remembering, that is if you did record attempts or remember your better runs, what you did one of the times that would've gotten you a better run, whether it's a better checkpoint time (check when time extension says "#.## AHEAD") or race time overall, and compare to it to how you normally complete a level to see what keeps you behind. E.g. I (donnaken15) was running Hong Kong Buoy on a livestream for a new PB, and found that saving super boost up to the second checkpoint at the tunnel to hover over a part of land with the boost was faster than how I would normally do it, going on water and making a bare turn.