Help me understand VE, strategy, fuel saving

Hi everyone, I need help understanding why this game that initially amused me is really getting frustrating.

I'm participating the "wec experience" intermediate license events, 40 minutes at Le Mans with doubled fuel consumption.

The race is basically 12 laps: my problem is that with a single pit stop (which is the strategy my opponents all adopt) I can't even complete the eleventh lap (I receive stop and go penalty for running out of VE at the Porsche curves during the tenth lap!). How the hell is this possible?

I don't think it's all about fuel saving, because I even set the strategy to +2 in the mfd, but when I start doing lift and coast I'm practically overtaken by the entire grid.

People who perform the same laptimes as me in qualifying (and as they do in the race), apparently aren't saving fuel, otherwise they should go slower (like me), or maybe they do it in a way that I can't really understand (yes, I watched youtube guides). Is there some "trick" I'm missing?

Help me understand how it works, please.