I notice a big black powdery stain collecting on my bumper after a week or so of driving. Is there a way to reduce it by leaning out the a/f ratios some more?

 

Black Soot is from running RICH , Lean it out!

 

Check this out... http://www.lancershop.com/customer/p...&cat=49&page=2

 

I wonder if I can make my own?

 

Don't touch the fuel settings, it's not from running rich, it's from running without cats. Once a week I take some Meguires cleaner wax to my rear bumper, it takes it off easily.

Don't touch those fuel settings, you were just tuned.....

 

I dont know anything about your car but if it was just tuned. DON'T TOUCH IT!! you would rather have to clay bar your rear end once a week than rebuild your motor I assume??!!

 

I am starting to think the soot has more to do with the length of the tail pipe and it's not having a downturn on it. No matter what tuning I have, my white bumper looks like an unwashed ....