Ok, I just bought an Actron and the GM cartridge that covers 1984-1995 (needs a different cable for the 94/95 Bonneville). Got the 12-pin cable with the cartridge. I have 90 days to see if I'm happy with it. I'll let you guys know. It was 140 bucks for the scanner, cartridge, and cable, with realtime capability. Came with a soft case, etc.
One hour later......ok, I'm happy with it. It'* a little on the big side, but it'* easy to drive with 2 thumbs. Tells me everything I want to know. Code scan, code lookup, realtime data stream, record data and play it back, etc. Very intuitive. Didn't even have to read the book. Only thing I can't figure is my boost % stays at 100 at idle. Haven't driven with it hooked up yet.
$140 for the scanner and gm cartridge.