Deal or no Deal

got a few questions that i hope all you experts can answer for me. I own a 90 318i wagon i have no idea what has been done to the motor but she screams. there's no obvious exterior motor work done and the rear gears are stock. it claims to have only 116 HP but i beg to differ. my old ranger pick up that had 200 HP and the same weight and it wouldnt pull me to 60MPH as fast as this 318i does. any suggestions? also i picked up what i thought was a 1991 318 sedan for parts (by the way i got it from this dumb blonde chick for 100 bucks) solid motor, needs and alignment, but other wise a great car that gets close to 700Km a tank my wifes rodeo gets mabe 500. well when i registered this car the itialians told me that this car was a 316. i have never herd of a 316. it has no badges or anything, i had to take their word for it. i paid less for road tax but will the motor use the same parts? like i said i got the 316 as a parts car but with that type of gas milage can i can just use the wagon for parts. is this a plan or am i wasting my time?

by the way a friend of mine has the exact same wagon as mine and his will only go 170KM at 5,000 RPM but mine will go about 220KM at 5,000 RPM