Recently I had my 2000 gmc 2500 6.0 liter truck start running rough. I changed the spark plugs, checked the coil packs and replaced the fuel pumpand fuel filter. Still no change....Any suggestions?

Check the fuel pressure at the engine and plugs for spark (ignition module).

The problem you describe is likely unrelated to the new coil pack. Rough running and stalling can be indicative of a fuel delivery problem, contaminated fuel, or one or more bad spark plug wires (or fouled spark plugs, but less likely). Readout all stored codes from the ECU using an ODB reader for a diagnostic starting point.

spark plug wires or coil pack

I would check the connectors on the coil packs, spark plugs and wires and replace them if they at all seem worn or tired. My 2000 sportage ran rough so I replaced the fuel filter, coil packs, spark plugs and wires, cleaned out the IAC valve, TPS, throttle body and intake tube, tightened the screws on the fuel pump access door under the right rear seat and cleaned the ground wire and the contact surface and I added 1 ground wire from the block to the firewall and 1 from the valve cover to the firewall. Your timing is more than likely right where it needs to be but the ignition may be slightly missing from a bad coil pack, dirty or fouled plugs or a bad plug wire.

if its running rough you should have codes stored, have you checked for them yet ??

may need 1 0r more coil packs replaced,or it could be what happened to my 2000 4.6---1 lifter expanded out and wouldnt collapse,causing the rocker arm to fall out of place and the valve could never open...try unplugging 1 coil pack at a time while running and listen for a change in the way it runs,if there isnt a change then its probably a bad coil pack,find a cylinder that runs and swap the coil packs,if no difference then its probably the valve staying shut.

make sure you put the right plugs in the fault is most likely the coil pack follow the plug leads from the spark plugs and you will reach the coil pack about £60

was anything recently changed on the car, like sparkplugs etc. this happened to my 2000 saab 9-3 after i put aftermarket spark plugs in, but if none of that just ask autozone to check it for free

What cylinders are throwing the codes?

What are codes being thrown, and their description?

How many miles on the SIerra?

Could be the TPI Sensor or it might be a touch out of timing.