E30 Zone

Hi all,

There's a rather large back-box on my 320 cab. I haven't had it very long, and it's quite hard to keep the damn thing clean because of all the soot coming off the exhaust. Is this a normal situation, or is there something wrong with the exhaust airflow? See photos below for an example of how it looks a week after cleaning...

I just made the images smaller. Didn't realise they were so huge first time around. Anybody any ideas? I'm not sure it's technical help I need, but this isn't really a styling or detailing question either, so here will have to do.

dude thats not that big man look at the one on my cab, but as for the problem maybe some fuel or injector cleaner might help out?