This problem started last week. I noticed a slight hiccup, meaning when I would give her gas off the line, she would wind down(like she was'nt getting any gas) and then she would takeoff. Gradually, over the course of the day, she started doing it while going 60 mph. I would have my foot on the accelerator, and she would slow down, RPM's would rise, and then she would pull forward, RPM's would go down. This became a cycle that it would go through every 2 seconds. It eventually gets so bad that I can't get the car to go above 45 mph. ( a quick history: bought the car a year ago, guy had car in garage up on blocks for 9 years, had left a few gallons of gas in the tank. I removed and powerwashed the tank, have since replaced in-tank pump, and replaced main fuel pump with used one.)I replaced the fuel filter last weekend.(fuel that drained out of filter was rust colored, I am going to by a new tank), and thought I had it fixed, but she started to slowly go through the whole routine, until I was once again going only 45mph I pulled off the highway, checked my voltage at the In-Tank pump, and pulled the pump to make sure she was whining. Checked ok. I wasn't sure if pump sock was clogged, so I tore a couple small slits in it(temporary, just wanted to get home).I disconnected and reconnected the ECU, same thing with the fuel relay(s). Got back in the car, and she drove like a million bucks. I don't know what she responded to though. I know the tank is my #1 priority, but what could be causing this "moodiness"?