Knocking/Clanking and Rough Running

[The Finance Guy]

My Ranger over the past few days has started to feel like its running on less than its 5 cylinders. I had been testing two of the electrical connectors on the injectors, so had them off (not the full injectors, just took off the connectors at the top), and it seems to be since then that this issue has developed. Presume I've done something that has caused the issue, but I can't see anything wrong with the two injectors, and FORScan isn't showing any codes. Could of course be coincidence...

Its starting fine and its idling ok, but when I drive and accelerate it makes a racket, and its just not feeling right. Like I said FORScan not showing anything obvious, except an issue with 1 glowplug which was there before and doesn't seem to be causing an issue. I have no warning lights or misfire codes. 

I'm going to maybe drop it off to my local garage, but just thought I would ask to see if anyone thought there could be something simple I'm missing?

Thanks