just put on a new exhaust system and was wondering if there should be what looks like black soot on the inside of the tips. is this common or is this a serious problem, concerning my engine?

 

Common; no worries. One day when you're bored, take a ride out to a parking lot; without looking too obvious, stick your finger in several exhaust tips of any auto manufacturers car. They will have this black sooty residue too.
Nothing to worry about unless you see black smoke when the engine is idling, or if you excellerate hard from a stop. This would indicate a overly rich fuel mixture. Have a buddy watch your exhaust as you excellerate hard from a stand still. If there is no black smoke, your fine.

Besides, if you were burning rich, chances are high you'd have your check engine light on, indicating a fault code identifying a faulty sensor or component.

If it's not a 5.4 liter engine, you can easily remove a spark plug and inspect it's tip. If it is sooty looking, that too can be an indication of a rich mixture.

Don't remove the spark plug from a 5.4 liter (mid 2005 and up), as these spark plugs are known to break at the ceramic insulator. I'd hate for that to happen to you just for this piece of mind check!

 

thanks i aprreciate the info. i do have a 5.4 so i dont think ill be removing anything until i absolutley have to.