My 1998 Astro LS rear wheel drive, about 115,000 miles, 4.3L has a weird fuel gauge needle vibration. It vibrates side to side a very small but noticeable amount, and quite rapidly. The fuel pump went out last summer, so I replaced the entire pump assembly, rather than just the pump, in hopes that maybe the sending unit was faulty(replaced with AC Delco), but it still vibrates, and doesn't matter how full the tank is. Any ideas?