Im blowing black smoke. Can anyone tell me how to fix it?
	
	
		Hey watsup everyone.
Yeah i recently noticed that im blowing black smoke and its sorta painted my rear bumper just above my exhaust. 
I think my fuel consumption has messed up a bit as well, im getting about 200km on half tank. Also when im driving and i go to change gear it sorta sounds like my car back fires a little bit, not a massive bang or anything, but its a noticeable noise that comes out of my exhaust. 
All the mods i got so far are just a full exhaust system and muffler. 
A friend of mine mentioned that it could be my spark plugs, and another mention it could be the injectors. Hehe personally im not sure whats wrong, but the black smoke painting my bump ain't cool... 
Thanks to anyone that can give me some advice.
Cheers, Lucky.  :D