Recently I put a 3" lift on my 2001 Sequoia and outfitted it with Skid plates and BFG KM2's. As a previous CJ7 owner, I know some really tough trails, that are wide enough to slide the "Griswold Family Truckster" through. Yesterday I gassed up and hit my favorite trail. In 8 miles, we gain 3500 feet, and it is very rough, very steep the whole way, rock crawling, bouncing etc. When we got to the top, I could hear what sounded like "boiling water" in the gas tank. I pulled the battery cable, thinking all the bouncing had caused the fuel pump to stick on. The boiling sound continued. I unscrewed the gas cap, and about a gallon of gas shot out, I put the cap back on, and the sound continued. I did this cap on/cap off exercise about 10 times thinking the pressure would normalize and stop. It did not. I finally put the cap back on, and walked away, wondering if I had some kind of fire inside the tank or pump, that was going to blow up. About two hours later I went to check, and it had finally normalized. Drove out the next morning without incident, and it seems ok today. Can anyone explain this? Is this a stuck valve in the EVAP system? The Purge line being flooded since we were at a steep uphill angle for so long with a full tank? I was scared ****less, I really thought we had a fire brewing. Any ideas?