Buick LeSabre 1997 - won't pass inspection - evaporator sys.

It has 69500 miles on it - I've had it for about 5 years. It won't pass NY inspection. I took it to the mechanic, and he did something, and said I needed to drive it around to reset the computer - highway is best. So I drove it and it still didn't reset. I drove it again yesterday, more than 100 miles (nearly 200 miles the day before), and everything reset except the evaporator system. What do I have to do to get it to reset so the car can pass???