Error code p0305

I have a 2001 Ford Escape that is running very poorly...No power, seems to be running in mud. I have a code p0305. I switched the coil packs on cylinders 4 and 5 and still got a p0305. I then switched the plugs / wires and yet again still have a p0305....
In addition I also have a code 1406?.....

Any suggestions?

Oh, I cleared the reader inadvertently and now am getting no codes. How do I get it to read them again?

vaccum leaks? compression good? injector pulsing? do you know what 1406 refers too?

Thanks for the reply Jeff Compton. This is what I've come up with for a p1406...."Differential Pressure Feedback Electronic Sensor circuit Downstream Hose",

I did notice this afternoon that there is a "hissing" sound when I put it in drive....So there is a leak somewhere. Just don't know where or what to look at as this is all a learning experience for me..lol......and after hearing that, the above description for p1406 makes more sense to me now. I just have no idea what to look for...

vaccum leaks and maybe and a dpfe or plugged port by the sounds of it!