When you had the tires shaved were they HOT from a 20 mile drive or cold? If they were cold, they might not really be round. If you shave a cold tire to get rid of the "flat spot" the next time the tire warns up that extra rubber that was pushed in becomes a new high spot as it flex's back out to normal. The process for shaving tires is to drive the truck to get the tires hot and immediately jack the truck up to take the weight off the tires. After it's in the air you can take your time before shaving as you won't be creating a flat spot.
Find a shop that has an old fashion tire balancer the spins the tire on the truck. This will balance the entire rotating assembly and also confirm the tire is really round.
Mike B
