My thoughts on a dirty filter. The pressure differential increases. Perhaps forcing more through it beyond some pressure. Opinions will vary of course. I also agree that a dirty filter will filter more out until the pressure differential really increases.

Any signifigant sudden increase in engine noise to me is important to locate. Generally I will not drive on it. Well if it is a sudden exhaust leak is one exception of course. Or I can identify the issue and determine that no further harm will occur by doing so.

Also if funds are limited. Change out a filter still working. Put the old one it in a sealed container and in the trunk. That way if your filter ever obstructs on the road. You have a usable spare to get going again. Fuel in general has to be cleaner today as long as you watch where you fill. So people no longer carry fuel filters for diesels in general. Yet it still does little harm to have one. Even a mechanic may have to wait for a replacement in many areas to come into his parts supplier. These cars are getting just too old to assume they will be in stock still everywhere.

This post is off subject as I just do not know what your problem is. You seem to have had a very sudden loss of power combined with a lot more engine noise. Just after accelerating hard. The noise remains. Yet on a power drop test all cylinders seem active. If the exhaust appears normal I would not check the injectors first. Even though they could remain suspect. Actually in a way you did test them. Any injector you loosened if bad. The excess engine noise should have decreased.

Old engine with perhaps old timing chain with sudden noise as you describe. Probability of it is not great yet it could fit the description. Usually the timing chains just break on these engines. So easy to eliminate one jumping as a possibility. You fortunately have hydraulic lifters that allow some give as well.

At top dead center the marks on the cam and harmonic balancer must line up. On their marks. If they are way off just turn the engine over 360 degrees one time more.

On one stroke or the other they must be on. Turn clockwise from the front. Or the hydraulic chain tensioner may have failed producing a lot more noise than normal. Combined with a one tooth jump somehow. A piece of a chain guide that broke off could do something like this. You could only have one injector fail in your scenario. Yet the noise remains when each injector was disabled. It is almost mathematically impossible for more than one injector of a mechanical type to fail at the same time.

A one tooth timing chain jump combined with a worn timing chain could equal light valve contact noise. It could also produce smoke and loss of power. Or no additional smoke. Depending on the engine design. Two teeth off on cam timing jams the these vintage engines up creating valve train damage and inability to run at all. Where a one tooth jump and existing chain wear could produce light valve contact. Plus the sudden increase in noise.

Believe it or not this could also be caused by a bad fuel filter. They have fooled more than one person. I am not a working mechanic but some on site have been or still are. Their intuition in general has developed over the years. Where I have little in comparison.