Ya mine was doin that this past summer... Ticking when you started the truck, then once the engine warmed up the manifolds, the ticking would go away.. turns out it was an exhaust manifold bolt.
Cylinders 7 and 8 are supposedly notorious for breaking exhaust manifold bolts.. the passenger side bolt broke on me.. took me like a half hour to easy-out it and fire a new one in.
Not even 3 weeks later the driver side broke.. that was a pain in balls to get.
If it is just the bolt for ya, i hope its on the passenger side bud