Just recently bought one of these to try out.
http://m.ebay.com/itm/161910688567
Tested on 1227747, 16197427, and my 94 Caprice wagon w/LT1.
Works as expected, good transfer rates etc.
Works with ALDLDroid, TunerPro, and EEHack.
There are others can't vouch for them.
If you buy a different one be sure it's FTDI based chipset.
Can also get same one cheaper from China vs. US seller.