You need the Actron CP9110 with the GM cartridge and 16-pin cable. The instructions for making the cable are here on this site (Bill Buttermore did the first one), in case you can't find the cable.
The cable for the 87-93 Bonnevilles is a 12-pin OBD1 connector that won't work for your car. 94/95 Bonnevilles are technically OBD1, but with OBD2 code formats and an OBD2 cable.
The OBD2 cable for the Actron CP9145 will NOT work on the CP9110. The CP9110 is probably the best tool for the money for GM OBD1 vehicles.
This guy is a bit high on price, but it might be a good idea to ask what cable it comes with:
This guy is a common seller of them:
But I don't think that tool comes with the GM cartridge or cable. His eBay store has them most of the time.