hey guys,
I'm super glad I found this forum. So I bought a 2001 Mazda Protoge MP3 on my 16th Bday a little while back, and I just grew into liking cars even more. I am really interested in getting to know and understand automobiles and I am just now beginning. I have many questions on my car and I hope to learn alot from you guys. I have owned the car for almost a year and Its starting to have a few issues. It has a little over 170k miles on it.

Issues:
-I believe I may have put in wrong grade of gas once, and now the engine is knocking. The knocking happens on startup, and then can only be heard from 2,500rpm and up. I feel like it has gotten slighty better and i may just run some engine cleaner through it. Any ideas?

-If the preceding issue seems to be bad, then would replacing the existing engine with a 6 cyliner be acceptable? This is also including that the car is FF and may not be able to control the torque.

-I am also wondering, but also doubtful, about turboing the car, since that would give better gas mileage and power to the car, if this is not worth it or not possible.

All of these issues are not concerning money, but experience. I am more into learning about the vehicle rather than saving money on it..

Thanks alot, and I am glad to be in this forum!