I'm new here. Home owner, we purchased the house about 4 years ago. Both inside units were replaced a year or so before we purchased the house. My downstairs system simply cannot keep up on hot days. Very little air flow coming out of the registers. Doing a little investigating prior to calling a service company and I noticed the coil in my attic is a trane model number TXC042C4HPC0. Looking at documentation online this model number is for a heat pump. My system is has a gas furnace not a heat pump. Can this mismatch cause issues? I also noticed the supply plenum is very small. Same size as the outlet of the coil but only 18" long with four flex ducts that take up both sides. Most plenums in my other homes were much larger that this one. Thanks for any info you can provide.