How to check mod lag? (1.7.1)

[Erik Mancha]

I knew of a few commands used in Tekkit classic to check for lag on certain mods, but those commands have changed and I am in dire need of a way for checking this in 1.7.1. I'm pretty sure that some of the lag experienced on my server is being contributed by mods rather than bukkit plugins. I get a constant 20 tps but I hear complaints of "block lag" from users. I can post additional information needed if someone is willing to help.