Translation: You are running rich and we cannot tweak the mixture any further to fix it.
Suggest that you do a search on this topic (mixture, injection, lambda) to educate yourself on probable causes. It could be the causes you named, plus the fuel distributor or warm-up regulator, or a combination.
You also ought to find an independent shop that you trust to do further checkout - these are very expensive parts to throw at a problem!
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe