The 1991 Ninety-Eight Service Manual indicates the presence of a Cruise Control Module - No Such Module Exists, as the Cruise Control System is PCM controlled.
In the service manual, the following references to the Cruise Control Module should be disregarded:
Page 9B-2 General Description of the Cruise Control Module
Page 9B-5 Outlines a Removal and Installation Procedure for the Cruise Control Module, and Figure 5 (9B-5) shows Cruise Control Module Mounting.
Page 9B-7 References to Electronic Climate Control (Section 1C). This procedure does not exist.
Vacuum tank removal and installation is referenced to Electronic Climate Control (Section 1C). The procedure is not covered in the 1991 Eighty-Eight or the 1991 Ninety-Eight Service Manuals. The following A/C and cruise control vacuum tank removal and installation procedure should be used.
Remove or Disconnect: 1. Vacuum hoses from tank. 2. Nuts securing tank to front of dash. 3. Vacuum tank from vehicle.
Install or Connect: 1. Vacuum tank. 2. Nuts securing tank to front of dash and tighten to 6 N - m (53 lbs. in.). 3. Vacuum hoses to tank.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.