I am having a similar problem. Its been a problem since the first print about 2 weeks ago. I have tried messing with extrusion multiplier values .96 to 1.15 and it still has gaps in the top layer as well as being fairly rough to the touch. If there was a way to slow down only the top layer and increase extrusion rate, it seems to me that might fix it. I would really like to have the option to add setpoints with different extrusion rates on a per layer basis just as you can do it the cooling tab. That would be so awesomely useful. Here is a picture to show what I am experiencing. The two grey parts were made with slightly different speed and extrusion multiplier settings. You can see the left one looks better. The green part is a really good example of just how sparse the top layer is printing. You can almost see 3 layers down. This one was printed at 100mm/sec and with a multiplier of 1.0 if i remember correctly. Any help with this would be greatly appreciated. Thank you.