Might just be because it's further away from the turbo and there is less heat from the turbo. The narrow band one wire sensors work better when there is more heat.
The back where the axel bolts in is totally different. And so is the fuel tank. And where the rarb bolts is. It's a totally different floor pan. Would have to do lots of welding and cutting to get the 95 running gear in a 91 floor pan.