What is the red thingy down the front of the auto shift lever on a Nissan Mistral?

Hi my Nissan mistral blows black smoke under heavy acceleration but OK under normal load Think this is normal for this type of motor but need to hear from other owners if this happens to them Cheers Noddy

Hi All
Just joined Have a Nissan mistral (96 model) to drag round behind my bus Very happy with it Will need some tips and general info as time goes by
Cheers
Noddy