I'd stop looking at the injection pump and figure out why your compression is so crappy on Cylinder 2. A 135PSI difference in compression between the adjacent cylinders is going to cause a NOTICEABLE "skip". The cylinder will still be partially combusting and contributing a bit of power, but so much less than the other cylinders that it will seem like it is missing out.

The maximum acceptable compression difference between 2 adjacent cylinders is somewhere around 10%. You're at 32%. That's a BIG loss of power, even if the injection pump is squirting fuel in the cylinder.

As suggested above, get a leakdown tester or blow compressed air in the cylinder and figure out where it's going. If you have a valve that isn't seating you'll hear the air coming out of one of the manifolds. If you have bigger problems you'll hear the air in the crankcase.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
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