Re: O2 sensor help...
You would have to check the signals at the ECM connector, if it's a different reading......time to do some wire tracing. Suggest you do a codes scan to get more information. If the .5-.6 vdc (rich condition for the ECM) are not being read, the system will continue to "add fuel" to the mixture, as you already suspect. LUK
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ACRONYMS:
LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That and the classic... DILLIGAS=Do I Look Like I Give A S***
1986 Mustang GT w/T-Tops 
NOW: 5.0L Stock SB, X303 Cam, 700 cfm DP Holley, 289 '66 Heads, 1.7 RR, Richmond Gear 4+1 Tranny, Centerforce DF, 2.73 Gears
WIP: 3.90 Gears, LS Overhaul, Adj. LCA's & UCA's (Granatelli), T-Top weather striping and rear braces bodywork 
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