I have a 3100 psi. That 4200 may be a little over kill for gutters.
If you touched a older shingle it would cut it almost in half lol.
I also forgot to mention that pressure washing out the gutter can create a substantial mess. For us it’s really turned into a last resort. The clean up alone can really take some time. Plus the customer sees this huge pool of sludge spewing out everywhere. I feel like they probably panic a little lol.