my rear bumper is turning black from the exhaust......i tried numerous things but still turns black this happens about every 30-40 miles of driving. WHAT COULD THE PROBLEM BE??

 

Excess fuel from your engine running rich; happens to basically every 5th gen out there (don't know about the 4th gen's). Get an engine management system (like Hondata) and tune it; you'll gain performance and get rid of the nasty soot.

 

o2 sensor
EGR
fuel pressure
fuel filter
fuel injector
spark plugs

could be a lot of things and we cant help you unless we know what you have done to alleviate the issue.

tuning will not fix an engine that needs maintenance