"that stuff" is not very descriptive which makes it hard to give any worth while answer. I will asume the "stuff" you are talking about is the antichip coating on the rocker panels. Apparently some years had body coloured rocker panels with the grey coating over the top. With only some light Googling it would seem your best bet is "castrol superdegreaser and some harsh rubbing"
I think your best bet will be to get on Google and search as there is quite a few e36 rocker panel how-to's.
Thanks for the up , I should have put my location on , "castrol superdegreaser " as far as Im aware isn't available in England I was hopping an alternative was available. "that stuff" was a bad description.
I would think that any degreaser would work. I can't see any reason why Castrol's would be better than anybody else's. There was also mention of using light scourer pads to aid in the scrubbing but if you have the rocker covers that are body coloured underneath I can't see it as a good idea. Have a look at this link; [url]http://www.hobbytalk.com/bbs1/showthread.php?t=212726[/url]