We have had a Di for 3 years now and are plaged with hickies in the red and blue units.
We do keep a clean machine and maintain often but cant seem to keep them away.
any help would be great.

I dealt with this same problem for about 6 months following the installation of our 5634 DI. Try this...
First make sure inking rollers are adjusted properly. It's very important to clean the silicone waste collection bags and wash-up knives. If there's any dried ink on the back of the knives it will eventually end up on the plate. It sounds like you keep a clean unit so you've probably done all this.

Ok, here's the magic trick. Apply Prisco Paste to the rollers once a week after wash-up. Let it run into the rollers for about 10 minutes then wash up again. Sometimes I'll let it sit on the rollers over the weekend then wash it off the following monday. Since doing this I have had almost zero problems with hickies even on solid blue or magenta jobs.

Hopefully this works for you... happy printing

i found that bringing up the sweep and lowering the keys helps... every time i had the keys opened big it was like opening the hicky floodgates.