I have a '94 7.3 vin K turbo diesel. A while back it started losing some power on hills. As in I'd put it to the floor and get nothing sometimes, just plug along. Other times it would respond as expected and power up the grades. Two days ago it started sounding louder, both at idle and working, same general sound just louder. Yesterday it started the 'clacking' while at idle and power, jumping from normal 'quiet' operation to being really loud. It happened for various durations at various RPMs. For the last couple miles getting home it also started surging and coughing like a plugged fuel filter would do. Not bad or constant but noticeable. Until then it was performing fine just loud. I've been having an issue with bad fuel and have changed the filter multiple times in the last few months, including yesterday after the issues just to see. There was no change. The only other thing I've done is top off the oil. I'm not what you'd call a mechanic. I know how to do what I know how to do and am picking up more all the time. Not sure if this is something I'd want to tackle but need to figure out what the issue is first. Any help would be appreciated.