tsls

[ulfa]

i want to ask about tsls and elasticity

1. if we want to cure the autocorrelation, are the instrument variable have to be first differentiate also?
2. to know the elasticities, we can use LOG to the equation. are the instrument variable also have to be LOG-ed?
3 if we want to cure the heterocedasticity in tsls , which one I should use? white test or weighted TSLS?

thanks, soory if my english bad :D