Most vehicles when new, do not have exhaust manifold to head gaskets, both are new so no issues, the problem is after the engine has cycled through numerous cold/hot cycles, when you remove the exhaust manifold it will warp. That's why there's tools like exhaust spreaders, etc and that's why gaskets are available.
Is it possible it's a lifter tick, or fuel pump? If you can get a buddy to set the park brake, put it in gear and apply a bit of throttle (careful here!), then you could be under the hood with some type of stethascope and search around for the noise.
Just an idea.

 

Road Hammer is right. I was thinking lifter ticking too. No bueno! You'll be able to narrow it down to the exact area with the stethoscope. If it's the exhaust leak, it will be far less noticable with the stethoscope than if it's a metal to metal ticking.

 

If you don't have a stethoscope, you can use the "Farmers Broom Scope", a 3-4ft long broom handle end held tightly in one hand forming a chamber to be held to your ear. The other end touching the suspected faulty part or area.
I have used this to locate bad bearings, lifters, broken crankshafts, noisy/dry gear sets, timing chain rubbing thru chain cases and sometimes leaking exhaust manifolds. You may have to move the FBS around a bit to touch/locate the noise source.

Good luck with your new truck, sounds like a diamond in the rough!

sprntpshr

**Safety note/disclaimer Do not touch the FBS to anything that is turns**

If you try to find that squeaking fan belt by putting the stick on a pulley, Well I told not to.

 

Haha thanks for the heads up ill try and stay away from the moving parts. The reason I don't think its a lifter is that it idols perfectly with no noises and even at some rpms while driving. Ill try and pinpoint it this weekend but if I don't have any luck its off to the mechanic! Anybody in the northern virginia area wanna come take a peek?