Luckily this was in a warehouse so I had plenty of room to work.
Complete change-out of duct and system. Old duct was molded and falling apart duct board. Replaced with round metal and improved the CFM so much I was able to lower the fan speed too cut down on noise. The customer loved the new quite atmosphere. It's just a 3 ton builder model, nothing fancy.
125' line sets
Raining all day
Working by myself without a service manager up my ass...priceless.