I took a long 9 hour trip. I took a break about halfway through the trip, and noticed that there was a loud "hissing" sound seeming to come from near the exhaust below the car.

After I ate with the car off for about 30 minutes and started her back up again, the hissing was barely there, but quickly returned as I got going again. Now, during my short trips through town I don't really notice it. It seems to only be there if the car is on the road for awhile. Any ideas?

Thanks in advance for your help

2000 Isuzu Rodeo V6

Exhaust leak?