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This is concerning. Obviously two areas need to be looked at the pulmonary system and cardiac system...and they work hand in hand. With the respiratory system they need to look at upper and lower areas, but snoring is usually due to an elongated soft palate...which your vet can visualizes with mild sedation. There is surgery to correct this and would be the first thing I would have checked. The soft palate lays further down the throat and can inhibit air flow. If the vet does not find a problem there...the larynx needs to be examined...and then the chest (xrays). The heart is evaluated with the xray as well to start, but that may require more tests like an ECG.
I do think the first exam should be the soft palate.
Let me know if you have further questions.
Since your breeder is a vet, I would just ask about the elongated soft palate and laryngeal paralysis. He/she should know exactly what I am talking about...or if they feel this is a possible problem. I do agree about the heart tests...but they are much more $$ than looking into the back of a mouth! It never hurts to ask!