I'm new to this, and I love this site already. I have a 2006 f-150 4 door, 4.6 v8 I'm having speedometer bouncing and when I stop at a light it won't down shift sometimes so I receive little power. I replaced all the speed sensors, abs sensors, and reprogrammed the PCM. We still can't find the problem! I put bigger tires on it, could that be the problem??