Won't go over 45 mph without knocking like mad. Popping codes too. Caan anyone help?

[Hyjaxx]

The car won't actually go over around 50...well I haven't tried to really. It gets a strong motor vibration and feels like it's running on 4 cylinders. It knocks like crazy then you take your foot off the accelerator and it stops knocking. It also knocks when you put it into gear and idle it. Not as bad in park but you can still feel that there's a problem. I read the codes and popped p0300,p0302, p0302, p1472 and p1470. I changed plugs, no fix. I switched the coils around in the front to see if one was bad and the trouble code started following the 1st cyl coil. I replaced that. The engine runs very smoothly until it hits 45 then it does the same thing. The new code is p0302- so it's saying it's a 2nd cyl misfire, and the p14's are still there.they are all pending codes. I also have emissions related codes for sec air, comp, fuel and misfire. I don't have emissions testing but I wanted to be thorough and state everything. The first time the car had the issue the cel came on, I turned the car off and both the CEL and the problem went away. I read the code anyways and it popped the 14's and that there was a 5th cyl misfire. I changed the plug only in the 5th because of time constraints and it was fine for a week. Then it did it again first thing in the morning. Now it happens 100% of the time. What do I do now? if it stuck with one code, I'd be fine with replacing tons of stuff to diagnose but this is getting out of control.