I don't know CDMASTER but does it let you set the gap between the audio tracks? If yes, set them to zero. If this does not work, try burrrn, burnatonce or Feurio (all free) for burning the CDs.
P.S.: You did burn in disc-at-once mode (and not track-at-once), didn't you?
EDIT: Maybe I've gotten you wrong - are you complaining about gaps between the tracks or during the tracks? If the latter is the case, forget what I wrote above. It could either be a bad burn (try high quality CD-R media like e.g. Verbatim Data Life Plus) or that your car player has problems reading discs >74 minutes. I'm pretty sure it's a bad burn though. Try scanning the disc with kprobe and see if there is a large number of C2 errors on it. If this is the case, use better CD media. In addition, it is usually better to burn CDs not with the highest speed. If you used 52x or 48x try it e.g with 32x or 20x instead and see if this solves your problem.