There's a number of sensors that control the air/fuel mixture and one of them measures the temperature at the intake manifold, so might be something there.
Below is a link that tells you (among many other things) how to do what is known as the "Stomp Test", i.e., read your own fault codes, which may help to diagnose the problem. The link is here:
http://tridem.han-solo.net/auto/erich/auto.htm
Also, try the E32 section of
www.roadfly.org., which has a large archive and excellent help as well for what seems like a common problem.