mlazzaro

I have a 1994 ford ranger with 90,000 miles 2.3l 4 cylinder with a 5 speed manual and everything is stock but a k&n filter. I got the truck 2 years ago and when ever I am on the highway and put it under load it starts pining and knocking and making noises that it should not be doing. I have tried my best to fix this problem and can not figure it out so I am bringing it to the forms in hopes that some one can help me out.

What I have done is
1.change all 8 spark plugs to bosh platum plugs
2.did 2 motorvacs (is supposed to clean the fuel rail injectors and all carbon out of cylinders)
3.ran 2 cups of water into a vacuum port to get rid of carbon
4.used 10 – 20 bottles of chevron fuel system cleaner
5.ran a 3m total fuel system cleaner kit ( does upper intake and throtel plate)
6.changed the fuel filter
7.changed the PCV valve
8.remover the octane spout plug that retards the timing 3 degrees
9.took out the MAF and inspected the little wires to make sure there was not crap or carbon on them

now this is everything I can think of to do I am out of ideas and I need some help. I pretty sure it is not carbon because I think I have ran enough cleaners to get any carbon that might be in there out.
the only thing I could think of is the O2 sensor but it is not cheep from ford so if anyone know how to test it let me know and I will. I need the pin out because it is a 4 wire heated sensor and I do not know what wires do what.

PLEASE SOME ONE HELP ME I DO NOT THINK I CAN TAKE THE PINING AND MORE IT IS DRIVING ME CRAZY