computer diagnostics with labtop
 

on a 91 z is there a program and a cable set up to scan my computer thur a labtop by conecting to the computer port under the dash

Check out Andrew Mattei's website here
He has both.

does anyone have this and how good does it work

I've got 2 of Andrew's cables and datamaster for 3 different ECM's.
All work flawlessly. Wouldn't have recommended it to you if I didn't trust him or the programs. ;)

thats good enough for me i will have to get ahold of him

You won't be disappointed. ;)