RV air conditioners are inherently noisy - probably the most common complaint from RVers. The duct work issue you discovered may not solve the noise issue. Picture may help others provide assistance.
RV aren't cars and will be impacted by wind/passing trucks etc. With that said it's a good idea to take your rig in and have it aligned (ask outfit if they have experience aligning Ford RV's) - correct tire pressure also will help. Also - OEM shocks on many rigs are cheap/terrible and yours are likely 14 years old. When I upgraded my E350 to Bilstein it made a nice difference in driveability. Should be lots of threads on this subject if you use the forum search feature.
