Catch can pcv problem

[Blackbird6]

I have a 96 Pontiac formula ltx and i installed a catch can with a breather on top. Im pretty sure the breather gives the car a vacuum leak but the engine runs great. But the vac leak is making the pcm give fuel trims up to 25% . So intried to hook up the pcv system without the can and i dont get the fuel trim but it runs like crap and loads right up like it has a vac. Leak. I dont understand what is going on. Has anyone else ever had this problem. And can 25% hurt anything at idol or even going down the road. I just wanted to put some time on the car before i get a dyno tune done but i wont drive it if fuel trim numbers can hurt it. Any info would be great. Thanks.