so I'm tired of all the cakes I've made it starts to buldge in the middle. so I decided to buy 4" deep cake pans so I can have a flawless look. I always add simple syrup to all my cakes, but with 4" tall cakes, can I? would it evenly soak? 

I cannot imagine ever being able to  bake a "Perfect!" cake in 4" deep pans.  There are enough problems baking in 3" pans :(   If the cakes you are baking are buldging in the middle then you are probably using too much filliing.  There are ton of threads on this site that address how to eliminate that.  Have you tried searching for answer to that?    

I put a very thin layer in between the layers and still it buldges..

Maybe there is something wrong w/your recipe.