Yes its possible. Insufficient timing for the rpm or mixture can put more heat into the cylinder walls and exhaust.
There are other possibilities too. But that is one.
How is the oil pressure at speed? If it drops after driving on the highway for a while, then it too is getting excessively hot and/or bearings are worn or similar.
Is it losing coolant?
On a vehicle without an overflow tank, the coolant level will be about an inch below the filler neck when checked cold. (Always check cold - never hot.)
