Once you remove the cover, the top nut can be totally removed to take off the remaining part of the cover.
Check on here for threads made by me regarding the 603 ALDA adjustment. I maxed mine and it was WAY too much. I have since farted with mine and it's okay now, good pick up from a dead stop and minimal WOT smoke (well my turbo leaks but that's another story...
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I have lots of good info in there regarding it along with pictures