Classic/Antique Car Repair: mazda rough running

Question
My father has a 1987 Mazda B2000 truck that he got at an auction.  He has gotten it to run better, but he states it runs rough when the outside temperature is warmer.  He says it runs better when it is cold outside.  Any ideas what might be the issue going on here?  What should we be checking out?  More than likely some emissions crap.  Thanks for any info.

Answer
He may have a small air leak in the intake manifold or
around one of the hose that leads to the intake. Changes
in temps will cause this problem. If it has a carburetor,
an adjustment to it could solve the problem. If carbs cars
the air temp on the outside and the humidity affects the air/fuel mixture.