what are sims for pyro probes?
 

I just need to know what sims for the pyro probes are, what do they do?

They fool your computer and keep your truck from regening when you remove your stock exhaust. They have 330 ohm resistors in them I think.

If you get an xrt or smarty you won't need them. If you don't care about being code free than get the sims and a cheap code reader from your local auto parts store and clear the codes on startup.