93 GSPD High Idle
Success! I took idle screw and idle mixture screws all back to zero, then set them to recommended starting points. (1 1/2 turns in for idle screws, 1 turn out for idle mixture screw) Which gave me a 3k idle speed, clearly too high. I then backed the idle screws out evenly bit by bit until I got to ~1200. Then screwed in the idle mixture screws until stumble, then back out to clean idle. Adjust idle screws, back to idle mixture screws. Go for a ride. Back to shop, hook up manometer and use idles mixture screws to get both cylinders firing evenly.
Just got back from a good 30 minute ride, and she now reliably returns to proper idle. Thanks for everyone's help!