need year, and engine size
Sorry, for idle speed no adjustments are possible, its controlled by computer.
The computer for a 1991 Chevy Caprice Classic is located behind the glove compartment. This provide a centralized location which gives a small level of protection to the computer.
its located on the bottom of the air filter
check g/box inhibitor switch could be out of adjustment
yes
Yes
Much like a 1975 Caprice Classic
None, there is no such thing as a 1998 Chevrolet Caprice Classic
Yes you can.
A Classic Caprice is a more upscale caprice, sort of like a separate trim level. Classics included small upgrades to the regular caprice, but not quite enough to warrant a trim designation.
Google 1999-2000 Chevrolet Caprice Classic.
I will assume that the car is fuel injected/computer controlled carburetor. You will have to replace the intake, the carburetor and the distributor. These parts can be found at your local junk yard. Care should be taken when selecting these parts, that they are taken from a non-computer controlled chevy. If not available, these parts can be purchased from a performance parts dealer, i.e. eldelbrock, MSD.