You're assuming 1 gallon of fuel consumed by a pickup truck emits the same amount as that emitted by a 2-stroke leaf blower engine consuming 1 gallon of fuel. They definitely don't.
Intuitively, this is why you can sometimes taste a lawnmower running the next block over in the air, but the same isn't true for a modern car idling, even if they were consuming fuel at the same rate.