I'm mainly an ls1 guy, but a buddy of mine has a pretty fast Impala LT1 and he noticed a problem when changing the plugs. The rear 4 are darker in color than the front 4 like the rear was running richer. Is there a cause for this that anybody can think of? Thanks for the help, Brian

 

intake leak...check the manifold gaskets of theyve been removed before...if not check the vac hoses on the t/b