Re: 2004 F150 Help - vibration / growling
All air intakes will be loud and have a 'sucking air sound'. My only guess if if they kit wasn't installed correctly, or parts weren't tightened down. If the noise was already there before the air intake, I'm sure the intake isn't the problem.
How long has it been since the plugs were changed out? My guess is that it might be an engine misfire but it's not to the point where it would turn on a check engine light.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!