While running rough you ought to be able to feel the metal fuel lines and get a good sense of which cyl is running rough or isn't firing (which I find highly doubtful). Once isolated, you can crack the inj line nut at the IP to prevent fuel getting to that cyl and see if RPM's change. That test will show you what a dropped cyl feels and sounds like. If there is no effect, that inj should be moved to another cyl to see if the problem moves with the inj or remains at that cyl. If the problem moves, the inj needs to be rebuilt. If it stays the problem is at that cyl or the IP.

You'll need a special 22mm inj socket, and at least two inj heat sheild crush washers. They are single use only.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)