1999 jgc couple of problems

Any ideas, jgc shifts from 2-3 high rpm hard shift, only the first couple times
when its cold. also only when cold, when you stop and take your foot off the brake there is a hissing air escaping sound inside around the brake pedal.
any advice would be helpful. thanks in advance.

have you had the flash programing done on the trans? i hear that is very common mine does the same thing. i need to get it in.