Last month I did the heads on a 1990 420 with a jumped chain. 132K and good maintenance. As part of the job, I cleaned and tested the injectors, and they were perfect. So I would replace the odd one and clean and test the others.

As to the stripped bolt, go buy a set of 6" hex bit 3/8 sockets. KD makes them and most good auto parts places will order them for you. When you use the right size, make sure than the tip is all the way down - tap it with a hammer to be sure - and drizzle a little PB Blaster around it.

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Chuck Taylor
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