Gti Mk2 engine power loss

[gtiguy]

hey guys first time posting

So i own an 86 gti 8v and i am experiencing a substantial power loss and i have no idea what i could be. it feels like i have lost about 25 percent or my power, it could be a little less, and my car is also using twice as much gas as usual, according to my mpg gage. the engine is also running with a deeper sound than usual, and the higher i go on the revs, it seems like im losing more power, and it very slightly hesitates when i hit around 4500 rpms, and it is difficult to get it past 5500 rpms. any advice would be of great help. thanks