99 GMC Yukon codes P0305 and P1345

P0305 = misfire cylinder #5
P1345 = crank position/cam position correlation.

First find out what is causing your misfire. Check that you speak at the wire where it goes to the plug. If you do then try a new plug.

The P1345 can be set of the distributor hold down bolt is loose, or if the crank sensor is bad. I think timing has to be set with a scan tool on these trucks. Try correcting the misfire to see if both codes go away.