'93 240sx - fuel/exhaust/other smell inside vehicle while driving

[wy2slk4u]

Hi,

While I am driving everything is ok until I notice the temperature gauge "shaking" back and forth. Then I smell some weird fumes inside the vehicle (with the windows closed). Smells a bit like exhaust as well as gas and something else which is seems to come in thick. The first time I had noticed this problem was "flooring" the vehicle from 140km and I turned my head to the back of the car...and INSIDE the vehicle was a nice cloud of smoke that didn't smell like oil but like something burning...I don't believe that it is an electrical wire burning...didn't smell like that. The weird thing is when I get out of the car... the engine smells normal and no smoke coming from the exhaust.

Any ideas.

Thanks,