If I run my car (S4 NA) without the split air pipe and the nipple it connects to on the UIM left open, will that create any sort of vacuum leak or anything else that will prevent the car from running properly? My split air pipe pretty much rusted completely away, I'm working on getting a new one, but I need to have it running now. I have also removed cats, air pump, ACV and rat's nest.

 

No vac leaks from there. All that will happen is air will be pumped out that opening at low rpms. Mine is disconnected since I use a rpm switche & solenoid for my 6PI. Keep in mind that no split air pipe means -25hp on the top end since the aux ports won't work.

 

Ok thanks. I have my ports wired open for now, until I can get a new split air pipe and come up with a way to connect it to my exhaust.