You should get grainy prints on high speed. Am I missing something here other than you think things worked better before your computer crash? Do you not remember the profile you used then? Are all your heads firing correctly? Have you done a bidirectional and media feed calibration for this print mode? Is your RIP taking over these settings without your knowledge?
Try getting a profile for the media/ink/printer/rip you're using from the media manufacturer. If that doesn't work, get one that is as similar as you can find. If that doesn't work, ask youf dealer for help. They should be very helpful if they're worth their weight in salt.
If that doesn't work, learn what it takes to tune your system to its potential. Yes, it takes time, effort, and sometime money. These things are easy to do poorly and hard to do well.
Sorry if I come across as another smart ass "this takes years" guy. But it kinda sounds like you're looking for the Make Perfect button. If you find it, let me know. I may be out of a job when that happens.
