The grease isn't for a mag. If it wasn't put inside the valve, its good to go once you get it cleaned off the bolt and spring. You don't even want light oil on the exterior of the bolt and spring. It just transfers to the breach area and onto the balls which causes big innaccuracy problems. If grease was put into the valve, you should clean the inside of the valve, but it may not be necessary. The mag tolerances are a bit tighter than most guns so the orings only need a moist coating for lubrication.
What do you mean be "running 5 shims in the valve itself"? The only shims in the valve should be in the ULT. Make sure you are using the 0.005" ULT shims and not the thicker 0.01" level 10 shims. You can use the level 10 shims, but you can only use half as many.
Erratic velocity can be caused by dirt in the velocity adjuster area or the regulator seat oring. A good cleaning of the valve is probably needed.
It sounds like your original problem was a bolt stick issue and can most likely be fixed by tuning your level 10 bolt. A carrier size that is too tight will cause the bolt to stick and results in the sear not rotating forward to reset the trigger. Remember to remove all of the shims from the powertube when you tune it. Don't put them back in.
Except for the Automag in front, its usually the man behind the equipment that counts.