Bad case of old socks smell.
Never happened in the SJ Bay area where the humidity was always high and tree leaves were a car cover. Now, in dry Colorado with no trees near the car, it has begun to reek.
Is there an entry/exit from underneath on the passenger side I can go upwards from carefully? Theres nothing in the big pan under the air intakes at the back of the hood, and I've pressure rinsed those.