Have just replaced the heads on my 2011 denali got the job all done and the truck blows black smoke so thick you can't see behind the truck and will only get to boutique 60mph. I have no codes, I have checked all intercooler tunes and boots, truck idles like a new one. Didn't not have this problem before heado replaced. Need little help from someone with more knowledge than myself please.

 

cracked injector? its very difficult to tell without seeing the truck