This is has been an issue for decades; manufacturer's published power ratings. There's been a lot of fudging and misrepresentation over the years. To fix this, the Society of Automotive Engineers came up with their SAE standard that requires a manufacturer to have their engines certified by SAE to be within 3% of the published rating, and that's not 3% +/-, that's 1.5% +/-. So if an engine is SAE rated at 300 hp, the tolerance is 9 hp; it can be no more than 304.5 and no less than 295.5. This is the engine by itself, not in the car. If an engine is SAE rated, that's how close the tolerances are to the published figure. I don't know if the Lotus is going to be SAE rated, but hopefully it is.
Due to the many components and assemblies in a car's powertrain, there's a certain amount of power that's absorbed by all those factors before power makes to the wheels. That's called drivetrain loss, and that can range anywhere from about 12% to as much as 17%, although I've seen more in some cases. If you take 15% just for an example, on a 300 hp engine, that would mean 45 hp is being absorbed in drivetrain loss, so only 255 hp is making it to the wheels. The weight of all those components; flywheel, clutch, trans gears, driveshaft, differential gearing all absorb power to get them moving. Then add the resistance from the thick gear oils used in the trans and diff.
This can be improved by replacing factory components with better performance components, like a lightened billet steel flywheel, lighter twin disc clutch, more expensive gear oils in the trans and diff, and a carbon fiber driveshaft if the car has an aluminum shaft.
By reducing the drivetrain loss, that increases the amount of power to the wheels without having to do a thing to the engine. In the above example, if you can lower the loss from 15% to 12%, that allows 9 more hp to make it to the wheels. If you can get it down to 10%, that allows 15 more hp to the rear wheels, so now 270 hp is making it to the wheels instead of only 255. In addition, removing weight and resistance in the drivetrain enables everything to move quicker, so the car will accelerate quicker and be more responsive to throttle input.
The quickest, easiest and least expensive of those mods is replacing the gear oils, and you will notice the improvement right away. Flywheel and clutch (with labor unless you do it yourself) is going to cost maybe a grand or two depending on what you get. However if you do make those changes, the car will feel more lively, and less like it's pushing against a headwind when accelerating.
Supposedly the Emira has a lightened flywheel, but we don't know how much more lightened. Hopefully we can get that info. I'm planning on at least doing the gear oil upgrade. I'll look into the flywheel and clutch later, if I feel the car could benefit. It may be fine without it, but I won't know until I drive it.