The Monark Nozzles are not considered High Performance Nozzles. They are just better quality replacements then the Bosch ones are.

In the Past the Monark Nozzles were like $22-$24 each. That was nearly 1/2 what the Bosio Nozzles cost back then. Since that time the cost of the Monaks has risen but still not as high as the Bosios.

Some People say the Bosios make more noise at idle. Some People like that and some don't.
I guess it also depends on the condition and state of tune of your Engine.

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84 300D, 82 Volvo 244Gl Diesel