91 xr2 has developed a sputtering hesitation when shifting.Cant even get past 3rd gear. But if I unhook 02 sensor runs great.I can even unplug TPS (check engine light comes on) but still runs great. Both 02 and tps never unhooked at same time. Just one or the other. Have checked everything I can think of. Plugs,wires,fuel pump,distributor cap,rotor,timing,vacuum lines,fuel filter. With this problem I have never had the check engine light come on. Just replaced 02 sensor so I know its not that. What could it be?