Engine power up, loss at the wheels down

[Gtom]

A tuning company I follow on social media put up photos of their before and after rolling road graphs when vehicles have been tuned, usually turbo diesels.

More often than not, the vehicle makes bang on it’s manufacturer power, or at least within a couple of bhp. What I have noticed quite a few time’s is that the losses have gone down by a few bhp once tuned.

Is there any plausible reason for this or is it all fudged numbers to look good?

One certain vehicle they same to be able to get 15-20bhp more than any tuning company.

Edit, no idea why the photo is fuzzy.

[GreenV8S]

Could be something innocuous like the transmission being hotter, but if they want the numbers to go up there are endless ways for them to make that happen without changing the actual performance of the engine. Getting consistent numbers is the hard part. If the company is publishing these to demonstrate their achievements, you should assume that the 'after' charts were created using Microsoft Paint.