Downsides of brewing espresso with high pressure? The Italian National Espresso Institute requires the following properties for a certified Espresso:


Water pressure: 9 bar ± 1
Percolation time: 25 seconds ± 5 seconds


I'm using a Quickmill Pegaso 3035, and for some coffees I do have a much higher pressure (around 12-16 bar). However, the percolation time is around 25 seconds, the coffee has a good crema and tastes fine.

Are there any downsides because of the high pressure? Does it alter the taste? Would I get more crema if I reduced the pressure?
A higher pressure is fine, as long as it is a controlled variable. You may have to tamp harder or start with a finer grind in order to accommodate the higher pressure. The increase in pressure otherwise would cause a faster brewing time and ergo underextraction of the coffee puck.

What's important is that you keep your pressure consistent. An occasional or erratic bout of high pressure makes your yield unpredictable.