A crushed and restricted exhuast will do that. Have you checked to see if you really hammered you exhuast? The O2 sensors just "finely Tune" the mixuture. The dont make enough of an adjustment that you'd notice that kind of power loss.
Check the exhaust closely, you might have a crimped section.
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64 1/2 "D" code Red Mustang Coupe.
Red Baron,
2000 Perf Red Mustang GT. 5spd. Stage 2 CNC heads with Large Valves, Comp Cams (270-274 dur .550 lift), Forged Crank, DRP pistons, Manly H-beams, Pro M 87 mm Mass Air, 24lb Inj, 75mm TB, Plenum Spacer ,Long Tube Headers, Homemade H-pipe, 2 chamber Flows, 4:10's, Steeda Tri-Ax, LKW 70/30's, Eibach Drag Springs, Steeda SubFrames, Battle Boxes, Rear Girdle, Adj uppers, Alunimum Drshft, Southside Lift Bars.
Project Cars, 64 1/2 6cyl coupe, 1930 Model A Nostalgia Rod.
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