57mercguy

So I have been working on my truck for a while now because of hesitation when i try to step on the gas. I can accelerate until around 1/4 throttle and any more than that and it bogs down and acts like it wants to die. I have replaced the TPS and the egr valve sensor and looking to replace the fuel filter later on this week. (if you have any clues as to why it wont accelerate, please let me know!) but anyways i was working in the engine bay and i noticed that i had a ground wire that was connected to the firewall directly behind the battery but isnt long enough to stretch to the battery. I am confused as to its meaning. I didnt know if it was something added by the last owner or if it was stock. Do any of you guys have a wire like that??? ill post a picture of it when i get home from work.. Thanks yall