Howdy Bob and All:
Since you have it apart, replacing the chain is cheap insurance. You said the current chain has 1/2" of slack, or deflection, check the new chain for comparison. And let us know. You might also do some testing on how many degrees of cam movement between the two points of slack. Chain slack, due to wear, causes the cam to act like it is being retarded. That is not near as bad as if it is being advanced- for performance. Chain slack, as the engine accelerates and decelerates causes wear to the cam gears.
Also check your rocker arm shaft to make sure that oil is getting to the front rocker arm and draining freely down.
Keep it coming.
Adios, David