I’d still take my chances with them in person than some random shop. He said he’d tune my brothers Frankenstein 2j swapped 240sx, so I’m sure he’d do the Link. With the power being so down, I bet there’s something up with the Z in itself. Seems like there more to the story than the car just randomly being down on power all of a sudden. We need to see dyno charts etc.
But yes I agree that you should have an ECU your tuner is familiar with, which is half the reason I went with a haltech