When i apply the brake on my07 chevy silverado the brake pulsation

Can you also you feel the pulsation in the steering wheel or the body of the car? If it is in the steering wheel then recheck the work that you did. Make sure that the hubs are clear of rust and torque the wheel nuts when putting the tires on.
To check if the rear are bad you can while driving down the road, lightly apply the emergency brake. If you feel the pulsation in the body then it is the rear brakes.
One last test that I have done is clamp off one brake caliper at a time using a clamp on the rubber line and seeing where the pulsation is coming from. Also if the antilock system is engauging there will be a pulsation in the pedal.

Read this post on what causes brake pedal pulsation. Hint: It's not the rotors' fault.
Brakes pulse when stopping Ricks Free Auto Repair Advice

pulsates ARE normal for this truck it means abs is working.
if truck pulls to the right then the LEFT brake caliber is not working right check to see if rusted up... also install NEW calb. BOLTS never reuse old one if one is bent calb. wont slide correctly

check rotor and brake pads. also check fluid level. one of those 3 causing problems.
more and likely its the rotor. its cheaper to buy new ones for around 20-30 dollars.
warped rotor will cause the pedal to ..pulsate. and more and likely you pads are wore.
when getting new rotor always put new shoes on so the rotor it can wear evenly.

You may see the abs light come on in your dash. I would plug a OBD II reader in and retrieve the codes.
I would say you either have a sensor that has gone bad or possibly a wire is shorting.
You can see the wheel sensor if you turn your wheels, and look down by the wheel hub bearing.
You can here the abs go whrrrrrrrr, when you step on the brake, and your braking flucuating.
Please let me know what you find.

did you bleed the brakes in the proper order? RR LR RF LF. check rubber lines for deterioration or BULGING when you apply brakes.

If you can test the car without the ABS module to ensure that the ABS is not the cause of the problem, If you have a spare module you can have it replaced for a while to test if the module is faulty,

One of the sensors has gone bad and needs to be replaced, the other thing to that would also do that is the ABS sensor is dirty or needs to be re gaped to the speed ring on the hub. There was a issue bulletin with your Tahoe on the ABS activating under 8 km/h. Good luck and hope this helps, if not clean out the sensor with brake parts cleaner and check the wire harness and ABS sensor bracket. Re gap the sensor to the speed ring hub. Here is the bulletin. Anti lock Brake (ABS) Activation at Low Speeds (Clean Wheel Speed Sensor Mounting Surface) #03-05-25-007C - (05/16/2006) 2001-2006 Chevrolet Suburban, Tahoe

check the rotors, go to a different shop and have them check lateral run-out and to check for parallelism of the rotors, if that is not it i dont know

If the new rotors were not allow to seat after replacement they will warp extremely easily. Easy to check. Remove wheel and check for trueness of rotor, a dead give away is if you see a blueish tint on the rotor.