Eta stumble

[Chessmaster]

Need a some help figuring out a problem on my eta, symthoms are random/ intermediate loss of power and drop of revs with car trying to stall. only correlation i have found is the installation of a new o2 sensor (mustang, used butt connectors) 2 weeks prior was fine intill now and with disconnection of said o2 sensor car acts normal. So im lost anyone wantot shed some light here? Thanks in advance

[Chessmaster]

Well i seemed to fix my problem, i cleaned the afm track and also the o2 connections( had coolant corrosion) and now its doing fine with 30+ mpg.