Unsure- My male cats breathing

Hello,
My black male cat, about 2 1/2 years old, is breathing oddly.. I'm not sure if there is something wrong with him, or if it's okay.

When he takes breaths, it sounds like he's stuffed up and there's some whistle sound as well. His nose isn't runny and he doesn't cough or look sick.. can someone please tell me everything about cats and there breathing, what it should and shouldn't sound/be like? What's a red flag and what this could be / caused by? Basically EVERYTHING I need to know .. yes I know a vet visit is the best to know what's going on but I would like to get an idea and some information etc before..

Thank you

It could be his heart, i.e., congestive heart failure. It could be an obstruction, i.e., a foreign object like cat grass. That whistling sound is a definite red flag and means a vet visit asap.

I counted how many breaths he took per minute and it was 23 , I read that 20-30 breaths per minute is normal anything over or under isn't . It's not so much a whistle noise, more like when you have a stuffy nose and it's that stuffed up noise.

could simply be allergies as well... hubby says Mikki does that sometimes...it's almost hard to tell if it's her purring or a slight wheezing sometimes.

When our other kitty Minnie was ill I had to take her in to get her chest drained when her rate would hit 40 bpm.

It could be an infection such as a viral infection, it could be a cold, or asthma. A vet could use a stethoscope and listen to his lungs, heart, etc. Whatever it is it sounds like he's having difficulty breathing and needs some medical attention. I'd keep him indoors and warm until you can get him to a vet.