O2 sensor problems

[Amish240coupe]

Hi, I'm new to this forum, didnt really try a search on this at all. But there is one thing I'm curious about. I have a hotshot header, OEM spec cat, and an HKS hiper cat-back, not sure if that means anything, When they installed the exhaust, they cut the ground strap for the O2 sensor, I didnt notice untill today. I was trying to figure out why my A/f guage was acting retarded, ran out of options till I thought about the ground strap. I couldnt get the bolt off of the heat sheild so I created a new ground on my frame rail and attached it to my Cat, but the A/F guage is still acting retarded, and I dont know why because I just replaced it about 2-3 weeks ago. By the way, I also have my guage wired into the wire immediatly off of the sensor, I couldn't find the wire to attach it to the ECU. Any suggestions?