I went and bought a 17mm and 14mm flare wrenches and loosened the connection at the fuel rail. The car had been sitting for about 3 hours. No fuel came out!? It was dry!? Problem? Is the "one-way" valve bad?

I am still waiting for my "wrecking yard" fuel rail and feed line stub to hook up my fuel pressure gauge, so I decided to change the fuel filter instead, though receipts from previous owner show it was changed about 9000 miles ago. Fuel tank was nearly empty. Used the "drop one side of bracket" method. Worked great BTW. Thanks to the brickboard for that! Gas had a bad smell. Like it gets in the lawn mower after sitting all winter. No apperent debris in the old filter. Got everything hooked back up. Turned ignition on, took a few extra seconds than normal to get fuel up to the rail and up to pressure. Wouldn't start on the first few cranks. Let it sit for a second. Turned key back on and it fired up. Drove down to the gas station. Still pinging at nearly every movement of the throttle. Gased up with 92 at a different station than I usually do. Car still pinging a bit as I pull out onto the road. I drive about 1/2 mile before, drive up the long hill back to the house. I realize that the car is not pinging. I tromp on the throttle... slight ping now and then but not bad.... As I drive it pings less. Bad Gas? Hmmmmmmmm? This morning, the car fires right up and not one hint of ping on the whole drive to work (mostly downhill, 18 miles and about 64 degrees) and there definitly feels like it has more power. Could the knock sensor be bad but the ECU is not be putting out an error code for it? I didn't have time to check for any new error codes last night. I will reset the computer before I head home this afternoon and see if I have any error codes when I reach home. Also, will have to climb the grade in 90 degree heat too so it will be a good test. I will keep you posted.