I have my friends off-road H-Pipe from his 2005 gt and I already have the H-Pipe on my 2006 mustang v6. I was wanting to put the cat deletes that went with it on but I noticed that there are only 3 o2 sensor holes on the cat deletes and I have 4 O2 sensors. Do I need both of my upright sensors or can I leave one unplugged?