I have a Lennnox 11ge furnace system, and problems with the AC line freezing up. I have had countless HVAC techs out over the years and have tried the old tried and true remove the electric air filters and use a standard filter, clean the A-coil, clean the unit outside, paid for loads of freon over the years....but what it all seems to come down to is airflow. My question: what is the most powerful squirrel cage/blower I can get for this type of furnace unit? I have been told I need more airflow....and of course, a new system to the tune of apprx. $7,000, which I cannot afford.