PET-G under-extrusion after changing the nozzle to a 1.2 mm d. one (Prusa i3 mk3s and PrusaSlicer v2.0)
Piecing this answer together from the comments on OP's post.
Myself and R.. noted that a layer height of 0.35&nbsp;mm, nozzle width of 1.2&nbsp;mm, and a fairly high feedrate (200&nbsp;% according to OP, no reference to what 100&nbsp;% is), is an exceptionally large amount of plastic to try and melt through almost any hotend on the market except possibly the Volcano, or the high-throughput version of the Mosquito. 

OP responded that lowering the layer height to 0.2&nbsp;mm seemed to fix the issue. That's still an impressive amount of plastic, but it's a 43&nbsp;% decrease in total flow compared to 0.35&nbsp;mm layer height.