@Kizzi. Hi I also got same tyres but in bigger size. Are you sure 30 pressure is recommended for Cultus? Does the door markings say that. There are min and max tire pressure written on the sidewall, try to find it and reduce pressure accordingly and then check.
Any tire inflated to full will give you a bumpy feeling and noise at khaddas.
The only criteria for the tires are that they should be fresh and not damaged during freight, rest is 19/20 difference between brands, no sea change should be expected. I have two friends who never changed their Xli and Gli's general and have no issues. They can afford better tires but say will get when stock tires are done.