Thought I'd have this taken care of by now, but the problem still pesters me.

Issue: rough idle, often jumps up to 900, or falls to 500 and starts vibrating. Car often stalls out, but it's not a rough stall. Just dies.

Items that have been replaced:

DISA rebuilt
VANOS rebuilt
New NGK plugs
New fuel filter
New VCG
ICV cleaned
Intake boots inspected (still good from what I remember, but having issues raises doubts)
Intake filter is new and freshly oiled
Oil is also new
Shell 91 gas only

No check engine codes.

73.5k miles. My assumption is fuel pump, but I have no issues with high-end fuel delivery at all, and my revs are always responsive. When I press the pedal, I always get power.

Possibly related: I hear a whistling noise when I'm not heavy on the gas. Pretty sure it's my intake, but I haven't noticed it until now. Might be a vacuum leak somewhere? Haven't checked my CCV hoses. No issues with oil consumption.

Up to this point, I've just thrown money at it because it was good maintenance, regardless. But now, I'm not sure what it is.