I really think you need to have a proper look at the cam itself. I would also line all the followers up on a really nice flat surface and see how they compare in height. They do look rough for 2000 miles, but not dismal.

With the cam out, you should be able to see characteristic differences between cam lobes, remember that Inlet and Exhaust lobes will look different from each other, but I still think you've probably got a fucked lobe somewhere.

Or, how about a completely random slant on it? My first ever fundamental CVH mistake 8 years ago was to assume that the tapping that I could hear from it was Lifters. I got them changed at a garage and the tapping was still there, turned out to be a blown exhaust manifold gasket.

Also, don't want to sound patronising, but you do know that the lifters should be replaced in the position that they came out of once worn in?