Hi,

With your marks of 90 in IAT you can definitely get a chance in IISER Mohali .For IISER-M anything above than 85 can be considered a safe score, you can expect your name in last rounds. In initial rounds cutoff don't go down 90. So you need to wait till the last rounds of counselling if the cutoff goes high. Hoping for the best. For more information refer to

https://engineering.careers360.com/articles/iiser-admission