Hmmm - EGTs do climb much faster after the boost quits - I take my foot out of it as it won't recover - just stumbles. As everyone who has replied to this thread understands these pumps better than I do, I can't argue with the air in the line theory. However, how would I get air in the fuel right at 13 psi of boost which it's been doing for some time? If you think a lift pump would possibly help, I'd appreciate any recommendations you could offer as to a good one.
The cheap 12V lift pump I had installed was an afterthought and from what I've read, one shouldn't be required. I should also mention that when I did have the pump installed it made no difference (I have it on a switch). Possibly it's not a big enough pump.
I do appreciate the feedback!
I've been supposing that the fueling cut is only incidentally connected to boost pressure, but what matters is fueling and load -- i.e., at 13psi you're hitting a certain fueling situation that's causing the problem.
As for air: if you have a small leak somewhere in your fuel lines, it may only become significant at a certain fuel pressure (when e.g., the pump begins to draw enough fuel to create a problem).
I'm reasoning here especially from the fact that you had a similar problem when you had a clog in your lines.
I feel like I'm grasping at straws here, though. I mean I don't know much to begin with, but am more than happy to help you brainstorm!
It might be interesting to try running with the LDA on the pump disconnected. I wonder if it's possible something very funky is happening when your pump responds to a certain boost pressure. Anyway, this is the only feedback system between boost and fuel, so possibly you'll get some information by separating the two.
Another test, which would be a bit of a hassle: You could try running on a container of diesel. Given that you had problems with clogs, maybe your fuel tank has some junk circulating around and causing problems?
Anyway, you'd have to find a way to secure a can of diesel while you're on the highway! You could lock your engine lid just on one side and put a shim on the other to allow a gap through which you could run a hose into a fuel can (strapped down over the engine). You'd want to filter it, of course -- I'd use a shop vac or similar to pull fuel through the filter and into a container.
These are all great suggestions. As you mentioned the LDA, that's why I mentioned a stiffer spring - the LDA is very easy to work on and any changes should show up in when/where it boosts and possibly how high. Obviously removing the boost line to the LDA pot should show a significant change.
I'm in the middle of repainting my truck right now but as soon as I get a chance, I'll do some tests and report back.
Thanks