89trknwby

I'm not trying to sound dumb but , I have afew questions. My truck is a 89 4x4 with a 22re, 5 spd. , 134,000 miles. I have had the truck for a while and haven't driven it much because I had a company truck. The a/c has been bypassed , to me it looks like some of the smog equipment is gone and there are some things unplugged. The main thing is the o2 sensor just below the exhaust manifold, it's unplugged. I have looked for the other side to the plug and I can't find it. Also, i have 2 O2 sensors and they are both bfore the cat. None after the cat. Can I wire the front O2 sensor in with the back ? There haven't been any codes with the front O2 sensor unplugged. It just runs like crap. It also has a little black smoke coming out of the exhaust when I rev it up. I pulled the plugs and they look like it's running lean. I'm going to have a buddy check my fuel pressure and timing this weekend. I have replaced the plugs, wires, dist.cap, rotor, fuel filter, air filter.I have also cleaned the TB and the MAF and ran some seafoam through it. As soon as I can afford it I'm going to replace the coil . Any other ideas why it would run like crap? My mileage dropped. Any ideas about the O2 sensor? Thanks for the help.