i have an 02 2500hd 4x4 duramax. after engine reaches operating temp if engine is allowed to idle for a few minutes or more, i get light blue smoke from exhaust upon acceleration, the smoke clears rather quickly and wont occur again unless truck is allowed to idle for 5 or more minutes. any ideas?

Did you check your air filter? Just changed mine, it was dirty and engine smoked when usually there is none.

yes its clean.the smoke is blue, that tells me its oil burning