After my research found out l8t cam can run on stock tune so i put l8t cam in my 5.3l made some changes in tune. It was running fine but i notice drop in fuel economy after 2 months. notice black smoke coming out every time i crank it [mostly at cold start] i am not an expert. i don't know if i am running rich or some thing else causing black smoke. i logged it, fuel trims seems high at idle. I really appreciate if somebody suggest changes i need to make. i am putting my log and tune file.

one more thing i had deleted 3rd cat put x pipe dual. had cat code 420, 430. so i disable my rear o2s.April14_7.hptfueltrimlog.hpl