okay installed mac headers and everything is tight no leaks. i also just installed 42lbs injectors. i kinda hear like a hiss type sound.. ??? do the bigger injector make noise? i have read alot bout the mac headers with the metal being so thin you hear the exhaust bouncing around. what do you guys think?

 

Try tightening your header bolts and flange bolt one last time to see if that fixes the problem. Flange might be leaky or check your egr tube and stuff.

 

yes i checked them already- also i have no egr..