Maybe try adjusting your temp as well. I know most people suggest using water right off boil, but that's usually for more medium-light coffees.

Since you are using a dark roast, lower temp can help.

Another factor is your water - are you using bottled, tap, etc?

Yes.. go to a cafe where you really like their espresso and ask what their recipe is: 2:1? Etc.

I would not use the robot by time. The nice thing about a manual is that you use your grey matter to control the extraction based on the rate of flow out. I tend to preinfuse at about 3 bar for about 5-10 seconds.. then start to ramp up to about 8.. I note that the extraction is roughly about 1 gram per second.. if it is much faster, I think you'll get sour and underextraction. Near the end as the extraction goes faster than 1g/s I reduce the pressure to compensate. I stop at my exact weight desired by looking at scale.

I suspect that you don't like that bean as espresso. But I'd also change your process to stop using time as your stopping point and control the rate of extraction by viewing the scale. My extractions vary from about 40-70 seconds. I think the beauty of the manual is the ability to not need to have it exactly 'dialed in (for grind)' and be able to finesse it via your pressure.

First of all thank you all very much! Even though I am not responding to everyone here all of this info is super helpful and I plan to explore your advice.

Made major progress today. Sourness is gone.

brew temp:96 deg
niche seeting:15
pressure: 9 bar
time:25 seconds
start weight 16.5 grams end weight 31.6 grams

It tasted good (way better than the same bean at my local shop) except for a harshness in the back of my mouth (perhaps this was bitterness but I really don't think so). Also the crema fell flat within a minute of brewing.

I am thinking this means over extraction and I plan to grind a bit finer and/or +/- 5 seconds on the time (not sure which).

Any advice from here appreciated as I am out of beans for the moment.

Cheers,