Have a 87 300td wagon w/ 124K.It has the new trap oxidizer replacement and has had a new complete head job due to the normal 603 problems. It has been running like a champ until today!

Filled up the tank( it was have full) :shortly after, it started to lose power as it was going over a Mountain pass. It now smokes very heavy white. It has not been a problem before.

Opinions please! I hope it's not the head gasket! Could it be bad fuel?