2009 Honda Odyssey vibration

Have a 09 odyssey after owning a 02 odyssey. The old one was silky smooth and this one has a vibration since new which I had the dealer look at and said he could not feel the vibration. Feels like it has a weak cylinder with vibration at idle as well. Gets worse dependent on weather, seems to be worse with hot humid days. The kids have conplianed of uspet stomach on long vaction trips which wasn't a problem before. Tires a balanaced perfectly.