Another update. It runs fine as long as I have Fuel Injection Cleaner in the tank. If I run on gas alone, it idles rough (cold or hot) and I need to step on the accelerator to start it. This makes me suspect my injectors. I've already gotten new holders and seals so I'll be replacing those one of these weekends. While I have the injectors out, I'll give them a good cleaning and check the lines to the fuel distributor. I also need to start replacing my vacuum lines. They are very brittle. I accidentally broke the one from the pressure regulator to the breather hose.
Occasionally, it will still hesitate when accelerating from a stop. Although, this doesn't happen nearly as much as it used to.
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino