Jim, Looking at it, I don't think the IOD will help to compensate the ENSO model too much. Certain characteristics, such as the strong peak at 1941, do not make a strong contribution. Many of the peaks do show up, but it is the odd ones here or there which reduce the correlation. IOD is also a noisier data set from appearances, so that doesn't help either.
I will post later, but the correlation coefficient is a bit above 0.4 for the model to IOD. It doesn't look bad as far as it goes.
It is definitely worth pursuing because it does address John's discussion topics of how linkages get propagated. paul