What could cause my max to idle rough? Timing is set perfect.

Don't know if you have a 4 or 6 cylinder, but I did find this for the 6 cylinder..... This is a copy & paste and does not come from me since I don't know anything about your vehicle. Clean the throttle body first. Bring the engine up to operating temperature. Check and be sure the base timing is set correctly. Shut off the engine. Ground the 'set timing connector'. Also ground pin #10 in the diagnostic connector. Start the engine and check the idle engine speed. It should be 750 RPM, + or - 50 RPM on non turbo engines and 800 RPM, + or - 50 RPM on turbo engines. If not, adjust as necessary using the adjustment screw located on the top of the throttle body. It is usually covered with a rubber plug. Remove the plug to adjust, then reinstall it when finished. Shut off the engine and remove the jumper wires. Base idle speed is now set.