I was stuck in traffic the other night and I have noticed all cars smoke differently. I'm talking about the normal grayish colored smoke that you can see when its cold. Does not smell like gas or oil, just a regular exhaust.
What turned my attention is that even newer BMW and other new cars smoke pretty hard sometimes and at the same time, older cars do not. My GSR smokes like that too.
So the question is - what is the reason for this smoke and is it cat related?

 

a good portion is actually water vapor. your catalyst combines hydrogen molecules (from the hydrocarbons) with oxygen molecules (from NOx) to form H2O. the NOx then forms N, while CO molecules are combined with oxygen to form CO2

 

So this is how it works, but why some cars do not smoke at all?
Does it depend on fuel quality? Well, I only use premium in my gsr...
The reason i'm so concerned is that i just tuned my car recently and i expect it to have perfect gas map and not to smoke at all.
Idk, im such a noob :D

 

the grade of gas you use shouldn't really have much of an effect on that.
cars all have emissions. it's a normal occurrence of a combustion engine. emissions will vary depending on the size, number of cylinders, emissions systems used and condition of the engine and emissions system.
if you're interested, just do some research. all you need is a basic understanding of chemistry and physics. fascinating chit

 

El Crapitan pretty much gave you the answer to your question. Suprisingly the new BMW's run very efficient. I have hooked up a few to the Four gas analyzer and got some very low consistent numbers out of them. Generally the newer the vehicle the lower the emissions are (More cats, more o2 sensors, awesome technology involving ecu's, air pumps.. etc). Do not confuse vapor smoke (a normal bi-product of combustion) with blue-ish smoke which is oil and white- ish clouds of smoke which is coolant.