Yes, you can just add a breather cap in place of the tube to the cleaner. But keep the PCV valve. My AC was toast, no freon in it. I have just removed the lines right off the heater box and removed all the AC stuff from the car when I redid the nose. It used to be a 81, now it's a 78
I kept the box because I didn't have time to properly weld up the heater hole in the firewall. The AC and non AC car's have a little different hole in the firewall. So, I'm still stuck with the ugly box, but I sprayed it Satin black like the firewall and it doesn't stick out as much..