No catalytic converters vs catted exhaust custom exhaust vs bolt on

What do catalytic Converters(cats) do? 

Pollutant gases are made of harmful molecules, but those molecules are made from relatively harmless atoms. So if we could find a way of splitting up the molecules after they leave a car's engine and before they get pumped out into the air, we could crack the problem of pollution—or some of it, anyway. That's the job that a catalytic converter does. This allows them to kill the odor of the vehicle's exhaust.  

What happens when I delete my cats? 

Once you delete the cats you free up some horsepower by allowing the exhaust to flow better. Now once you do this you will experience some exhaust smell. This will come with the smell of fuel or a strong exhaust smell. This is normal when you delete the cats from your exhaust. Having no mufflers will make the smell even worse.

Is my vehicle running rich or lean? 

If we tuned it our normal answer would be no, but if you don't have a way of reading AFR and/or O2 sensors that we can see during a datalog we can't tell 100% otherwise. This is why having HPTuners and being able to data log for start up, and up to WOT is very helpful. If you think it is running rich/lean this is the first step in checking to see if it is. This is why we recommend a wideband, Hptuners, and/or scan tool that can read your O2 volts.