Engine running rough below 3k RPM. Fine above it. ???

[chevy72blu]

I have a stock '98 LS1 in my truck which has been there for years. It sat for a while. t

There is a stumble and hesitation at low RPM that seems to go away around 2500-3k RPM. First thought was bad gas, but I pumped out what I could and I've ran a few gallons of fresh 91 octane. Maybe helped a little? Cleaned MAF and TB. No change.

It also takes several cranks to fire, whereas it used to fire on the first crank.

I would think any issue fuel related would be worse at high RPM.

Ignition issues? I was thinking maybe coils? No codes. O2 sensors?

The truck is down probably 100HP, but otherwise runs and drives just fine.

Thank you for your thoughts!

Edit: Pulled one plug, it looked fine.

OBD2 scanner shows good output from the O2 sensors (rear deleted).

Sitting in it at idle for a long period, it is definitely idling rougher than it ever did before. Stable, but bumpy, like a cam with a lot of duration (it is stock). Took it on another drive and while it was hesitating I floored it - bogged and lost all power until it recovered from that (engine did not die).

I feel like this should be fairly obvious but it's been a while since this thing was my hobby.