Smoke coming out of the exhaust is normal in many situations. The more restrictions you remove from the OEM exhaust, the more the car will smoke and the more it will smell. OEM's design the stock exhaust specifically to get rid of smoke and exhaust smell. So the more OEM exhaust components your remove, the more your car will smoke.
Two of the most common situations for smoking quire excessively is cold ambient temperatures and idling the car for 10+ minutes. Both of these scenarios create the same basic conditions inside the exhaust, which is moisture build up. Water is a byproduct of combustion. But when it's cold or you idle for a long time, the moisture builds up in the exhaust, the moisture collects any oil and fuel vapors and puddles them at the bottom of the exhaust tubing or in resonators and mufflers, then the water/oil/fuel mixture heats up and begins burning off. This is why it can smell like oil, smell like gas and have a color mixture between the two.
The colder the temp, the more your car will smoke. The longer you idle, the more your car will smoke.
