It's a while ago that I looked at the IMU's.. If I remember rightly it's to do with missing bits for the air conditioning blocks on top of the cars. The twinkles files don't work either. Try removing any smoke references in the config.txt. It took me ages to get them to work in TRS2006.
Can Somebody plz help me i have downloaded willamg's Imu For Trainz 2004 but I can't get it to work plz help