I had to pull the distributor out of my dads tahoe yesterday, 98 tahoe 1/2 ton with 5.7L V8 and auto trans. I had to pull the intake manifold so i could replace the intake gaskets. Anyways, i marked it, restabbed it. The truck starts up fine and idles fine but will lose power in the upper rpm's , above 2,500.
Im pretty sure the ignition timing is just too far retarded. There are no timing marks on the crank pulley.

How do i accurately set the ignition timing?

Not 100% positive, but on my 96, you need a device to read from the computer to set the timing. Most local garages have the proper scan tool.

Thats what i was thinking... but i wasnt sure of it. One of my buddies at work has a scan tool. ill try it tomorrow. thanks

just an update for those interested and for future reference...

I had to hook it up to a scanner and check the actual values to set the ign. timing.