Tried , got it also. 6000 poly 25 groups 12 materials (for a cube cars?) are exactly the things to not do as indicated in the doc. The author didn't even noticed the error message about perf or maybe he didn't care. (it's also infrige the last chapiter of doc about "respect users")
I balance now, I'm the first one to salute even the silghtest beginner efforts to make addon but here I think it's really what we might call an unfinished addon to be polite.
nembutalteam,
if you read this please rework a bit your car, you can do the same with 500 poly and one material and also lights at least, it's not difficult, as it is now it trigger an error message from universal cars.
Thanks
Dan