Just make sure you don't get fooled by any gimmicks they try on you.
Very recently someone posted on another forum that they were making 238 bhp after their car being mapped, just to hit a headline figure CPL set the rev limiter to 9,200 and ran it again, made 240 then set the limiter back to 8,600.
No point risking the engine due to cavitation of the oil pump to reach a figure the customer will never achieve again IMHO.
It might have been the customer egging them on, but I'm sure they'll do a good job. They do achieve some good results.