Yes! The Camber does go negative on most cars as they are lowered. The 124 chassis is often out of range in camber from normal settling by this time. I wouldn't worry too much about it....How negative is it??? This would tell me how low did you gooo.
The factors that cause the car to pull are either in the alignment or in the tires, good chance its the tires...nobody lowers one of these without also putting over-sized aggresive tires on also(bg). Switch them side to side in the front for diagnostic purposes (to save you a trip to another alignment shop). If that doesn't work you need to find someone who aligns cars. He** with the specs fix the problem, use what you have. The car is still adjustable. If you have to go more than 1.5deg negative on the left side you do have a problem.
The method to correct a pull with alignment involves making the Caster greater on the on the pulling side, in this case the left. You also can make the Camber higher on the side you wish to correct to, this case the right side. In other words no matter what the values your car needs lower Caster on the right and/or higher on the left. It needs higher Camber on the right and/or lower on the left.
Without driving your car I can't tell how much correction is needed, but I always know before I measure a car by driving it before. As a rule of thumb I would change the Caster differential by 1 deg to the right and Camber about half a deg. If you have your alignment results email them to me.
BTW since I firmly believe in MBs engineering talents, I have never looked into this market to see if the suspension tuners provide the proper parts. Normally when cars are lowered properly the spindles are re-arched. Check with your sources to see if anyone provides the parts to do this properly and the only real consequence to the high negative Camber will be tire wear. Depending upon the degree the toe can correct for this partially and the cost of repair could buy a lot of tires.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician