Inspected the ductwork and detected no significant leakage; howbeit the ductwork is not in great condition, and is leaking in some capacity throughout. There is indeed a detectable odor coming from the vents that smells eerily similar to that of the crawlspace. Ideally moving forward the ductwork should be replaced, as it’s condition is not comparable to the newly installed equipment outside. Additionally, it is advised to have the crawlspace sealed by a professional. This improvement will serve to benefit the home in many more ways than one, and should not be over looked. It is advised to consult a crawlspace specialist, and moving forward be in touch in regard to the replacement of the ductwork.