I changed my fuel filyer in my 1991 ls400 now the car runs rough at idle drops to abou 750 rpms at idle the when taking of slow until I hit second. Iy seemed to mis firing I did full tune up plugs wire caps routors colant tempetire sensor. I'm think a cloged fuel injector or even though fuel filter was replace last an is when the problem started any ideas would be great thanks.....