I have estimated a model with many interactions of both continuous and factor explanatory variables. The model is to be used for prediction.
My model has performed reasonably in out-of-sample testing.
However, I have found that my errors are correlated.
I took my fitted values of y and ran several regressions like this:
$$y\sim \text{fitted}(y)\cdot \text{explanatory variable}$$
There were many instances where an explanatory variable already included in the model was significant.
What are some good techniques to resolve this issue?
Side note:
I have no strong a priori views on what the "true" model should look like.