Need diagnosis of exhaust issue

My 1989 Mitsubishi Montero (in immaculate condition, was owned by the mechanic who sold it to me--I've had it for 3 weeks) kicks off lots of exhaust. Not bad exhaust where it is white from burning oil, just regular exhaust.  And it doesn't seem to be coming just from the tailpipe, but from underneath the front of the vehicle as well as the tailpipe, although I haven't gotten under there to look.  I surmise the exhaust is coming out near the front of the vehicle because it seems to well up and congregate, especially when I am at a stop light and I can clearly smell it EACH and EVERY time, but also while I am just driving around the city. (Is that normal?) I end up cracking my windows so I don't have to breathe it all in.   It is an easily discernable smell, like bus exhaust.  Invisible.

I am primarily concerned about it as a health issue.  I smell it and breathe it in ever time I am just driving.  And so I start to wonder what undiscernable levels of exhaust I might be breathing in that I'm not able to smell due to lower concentrations of the exhaust and what the cumulative effect might be over time.  It can't possibly be good.  I have taken 2 long trips with this of about 3 hours round trip and didn't think the exhaust would be an issue because theoretically the exhaust would just tail off into the wind behind me.  However,  my chest hurts the next day after these trips, which I atribute to a steady amount of exhaust entering the interior (My theory).   I am probably breathing in the exhaust the entire length of the trip.  I think it creeps up and in somehow from somewhere underneath, which further makes me think the exhaust is being discharged from another area underneath the vehicle other than out the back tailpipe.   

I have had no mechanical issues or performance issues or strange sounds associated with this.  No white exhaust, etc.

I think there is something that can be done to correct this because I can't imagine that this is normal and that they sold the cars off the lot in 1989 with this condition.  Does anyone have any ideas on how to approach this issue???

Other info: The engine was rebuilt by the mechanic and has about 30,000 miles on it.  It drives like a car.  Atomization was added to increase gas mileage, etc.  My mechanic knows every inch of this vehicle.  But some collective wisdom might help advance my thinking on this before I approach him.  I am greatly appreciative for any theories.

Thanks very much.

I met with my mechanic.  The smell of "exhaust" appears to be coming from a leak that is making the coolant burn.  The leak appears to be small but the tank was still dry.  It will need a new radiator, the mechanic said.  He told me it would not be expensive because the Montero's were built so that parts could easily be changed in the field (ie African bush) and that radiators for Montero's are plentiful.  Additionally, he offered to pay half as he didn't expect this to happen with this vehicle and said that he stands behind the cars that he sells.