HH/AQ had a bad lot of nozzels come through, I don't know when it started or when they figured it out and fixed the issue. I assisted the tech who did my service and it smoked like a old coal fired plant. After I got through with the HH certified training, they gave me a new nozzel, and I changed it when we got home. Works perfect now. The rubber boot WRV installed was not necessary, and they put it on I think to keep critters out of the coach. If the air intake does not extend about 1/2-1" below the bottom of the coach, I would add a little bit of pipe maybe. There is also a air shutter adjustment, and it's best to adjust it by sound, a qualified tech will know it's best setting. HH did paint some red paint on the spot they tested the unit to so you can also use that point to set it too.
Monty & Janet - 2007 Alpine APEX 40 MDTS
S/N - 75715 - Retired - Master Certified RV Tech