When talking about your deck to opponents, you can also call it 'Quatman', without pronouncing the 'u', to confuse everybody. This is very efficient in a tournament setting, and fun in casual play at your local store.
Your Rig should be : Atman@4 + sucker(s) + Mimic + Yog + a free memory for parasites + whatever you want, you're an adult. You don't need me to hold your hand.
The first version of the deck had Spinal Modem with complementary akamatsu memchips, but I felt during testing that a second SMC was absolutely necessary. Hence the upgrade to Grimoire, which give a nice bonus of +2 MU, and a small boost to late game parasites and mediums.
The retrieval runs are there because having some kind of Archive pressure is always best. You want them to have an ICE installed there, and you want to force them to rez it.
Another detail, Retrieval Run is not seen as an economy card here, but as a recursion card.
Last detail: Why is Retrieval Run good in this deck and bad in pretty much any other deck? Because you can retrieve a card during the same turn it got dumped in the heap (with Inject), without letting the corp react. The only other way to do so is to Scavenge something to install another card from your hand, or to use Freelance Coding Contract.