In my opinion there are people that have the equipment to analyse, compare, develop and optimise port shapes/sizes and there are people that build engines, have a die grinder, and say they can port a head.

Unless they have a ticket from the recyclers showing where they weighed in all the scrap YB heads that they did the development on, a flow bench in the corner and some very accurate documentation of their port designs and results i wouuldn't go near them.

I would stick with somone like cnc heads.