I haven't done the above mentioned check of IPR and ICP%. I had a low/intermittent voltage issue with the truck. I replaced the alternator and that didn't do it, then I found the other connector on the alternator (I think the regulator) was bad, so I got a new connector and changed that. That seemed to fix it and I'll drive it some more tomorrow to see how that addresses the other issues.
I've been having two issues:
1) The truck doesn't seem to want to start when hot. If it's running, it's fine. If I shut it down and restart within a few minutes, fine. If I wait 15 minutes, it seems to need to wait another 15-25 or it won't restart.
2) The truck has bad lag off the line, and doesn't seem to have the midrange torque that it should. Boost looks to be fine, but it just has bad engine lag (not turbo lag). Idle to 1,500 RPM with it in gear is painfully slow, and it barely even sounds like it's trying to move. Once it gets above 1,500 it responds normally, but still doesn't feel like it has the midrange it should, and then does well at top end. My Excursion with a V10 in it (and basically the same gearing) feels much torquier.
These symptoms are making me think that this might need an IPR. In both cases low oil pressure on the high side could cause the problem observed. I had thought the voltage might also be a contributor (insufficient electricity = injectors can't open and close as well as they should) but a quick test drive didn't seem to show any difference. I may see it working better tomorrow.
Even when we got the truck I didn't think it had the mid range it should, and that hasn't changed. However the lag off the line has gotten significantly worse in the time since we got it as has the hot start issue. I don't know if this is typical of an IPR or something else.
Oh, and if I buy a new one, I'm figuring the genuine part only for something like that...
Any ideas from the 6.0L gurus?