"My new car was to be delivered today but..." means the car's delivery was expected today but it didn't happen because...
"My new car was to have been delivered today but..." means approximately the same thing as the above, however, putting it into the perfect makes the statement more formal, and consequently stronger, and suggests some irritation on the speaker's part: the car's deliv
No significant difference. To my ear, the first one seems to be said at a time much later after the expected delivery than the second one, as if the speaker of the first statement were more resigned to the fact that the delivery would definitely not happen.
Nevertheless, I may be deceiving myself about this.