I don't think the coil will help unless you also replace the airhandler as well. If by modular homes you mean mobile homes, the duct system under the home is usually all the same size from front to back. This generally requires a special type of airhandler & evaporator coil that works at a high static pressure. Nordyne, Coleman & Intertherm are that main ones i can think of. If you decided to get a new coil, make sure you get the "M" or "W" style coil with the expansion valve. These new style coils can handle the extra refrigerant that most new 13 seer units need to operate correctly.

Hope this helps

I have seen a couple of re-designs over the years. When the volume was increased with a larger duct, the system seemed to cool much better. If the HVAC system started with a smaller coil, then you may not get enough air past the coil. This will cause freezup. The only to combat this condition is to increase the duct size. Like was said before, the HVAC air handlers in a mobil home are usually a high static pressure system, that is crammed into a space inadequate for proper operations.

Thanks guys. Today was the first good hot day and it still was tring to freeze up. It looks like I am going to try one of the "M" OR "W' style coils. This is the first time I ever had a problem with a new system not working. Again thanks for the advice.