The furnace exhausts to the side of the house and has another PVC pipe on the same side for intake air. The furnace locks out frequently with 1 flashing LED code. I thought I could smell gas so I called the gas company and they told me too much gas was coming out of the exhaust vent. Called a technician and he said it needed more ventilation air because it sits in a small utility room. So I had a 16x16 grill installed in the room. However it locked up again. Flame is mostly blue with yellow flashes. Any ideas as to what is going on?

Sounds like you have a blockage on either the in or out pipe. If it is a sealed combustion chamber (indicated by 2 pipe system) the air in the room has nothing to do with it