Engine stumble when in park or neutral
I recenlty installed a K&N FIPK for my 2005 4.0 supercab Ranger. After installing I wanted to rev up the engine to listen for any odd sounds, and of course just hear how the new intake sounded. When the engine hits about 3000 rpm in park, or neutral it stumbles/misses, almost like it's going to die. The odd thing is that it doesn't do it while driving, I put the transmission in 1st(automatic) and went well over 3000 rpm and didn't feel or hear any hesitation/misses. I also accellerated quickly a few times(causing rpm's over 4000) over the past couple days and noticed nothing out of the ordinary.
Any ideas on this? Unfortunately I had never reved the engine in park or neutral previously to know if this has always been an issue.