i have a nissan FB14, model 1996, Petrol, Automatic transmission car. when i go a mountan road, top of the mountan, caming large white smoke from tail of the sylencer. running of the car is normal. (no mis in the engine) in that time i have to slow the accelerator. after one minute car comming normal.

when going on the flat land, nothing any problem.

my problem is coming only on the mountan raods .

pls advice me