So after a little looking around a little it would seem that on “newer” 240s that use the Bosch LH 2.4 ECU the timing of the ignition is a function of the computer rather than the position of the distributor. This means the timing light is not going to help me out. So why the rough idle? It could be a leaking intake manifold gasket as demonstrated by this video. After I install the new relay this evening I’ll try this carb cleaner “trick” to try and find any air leaks and see if that’ll help.