Heading toward Injector Replacement

[hookliftpete]

This is an ISC on a Pete 335. I'm thinking I need a couple of new injectors.

So far, have replaced the Imap, Differential pressure sensor, checked egr valve, cleaned egr pipes, etc, and most recently replaced the dpf. After all of these, the doc is still face plugging. Oil sample shows no coolant in oil, just normal wear on the oil, aside from obvious excessive soot.

Also, have performed a cylinder cut out test, running the engine on each cylinder individually. 1-4 ran fine, maintaining ~700 rpm with no issue, 5 and 6 both struggled to keep 500-550 rpm, and sounding close to stalling.

With all this in mind, I'm planning to replace injectors on those two cylinders. Does this seem like the next logical step? I have not replaced the exhaust backpressure sensor, figured I'd do it with the rest of this project.

Which direction are the cylinders numbered, #1 at the bumper or the firewall?

Also, how do I bleed the common rail system of pressure?

I'm sure there are other things that I'm missing in this process, as I've not done injectors before.

As far as what 'supplies' I'd need, a valve cover gasket, new injectors, are there other gaskets, etc that should be done meanwhile?

Thanks for the help...looking forward to learning as I go.