Critical Path of Processor

[Tom George]

I was wondering at what stage of the processor (using the WithNMegaTapeoutBooms configuration) could the critical path be improved? I remember reading somewhere (probably BOOM v2 docs) that the critical path was at the issue stage.

If I choose to make changes to the Chisel code to see how critical path could be affected, how do I measure the affects those changes would have on critical path?