tire hum/ wheel noise?

okay my dad and i own an '03 seqouia SR5
and so far
its been a POS drive train is great chassis is great ride is great
but the electric system is crap
and the body work isnt the best
any way

we started having this humming almost like a pulsing sound that at some points vibrated the vehicle coming from the right front tire area

it wasnt a constant hum but like pulsing in and out at all speeds
at higher speeds 55+ it made the vehicle feel unstable but that was prob mental also while braking it got quite noticable and would sometimes shake the car.

we took it to the dealer and they said NOTHING WAS WRONG
they have also said this about our faulty catalyic converters and refuse to replace them

anyway

they said nothing was wrong and when we got the car back
the noise had vanished
with in 3 hours of driving this thing again
the noise was back same as before

idk if this helps but it seems like the ABS kicks in way to early like stopping under normal conditions

thanks for any help
gabe