I am performing a Stochastic Frontier Analysis on unbalanced panel data in R with the package frontier (based on Battese & Coelli 95). I wonder how can we check for autocorrelation / endogeneity. The residuals() function returns the residuals, which consist of both the noise term and the inefficiency term, i.e. residual = y - f(x) = v - u. I am not sure if one can use these residuals to test for heteroscedasticity (Breush-Pagan test) or autocorrelation (LM test). Have you seen this in the literature?