01 Impala long crank after sitting 5+ minutes

My '01 Impala with the 3.4L engine has a slightly long crank if it sits for about 5 minutes up to a couple hours. Sometimes it will start right away and die (maybe "crank fast enough that I let off the key" would be more accurate than "start and die") then start immediately on the next attempt, other times it has to crank for 2-3 seconds. It doesn't do it every time, but probably 90% of the time when it sits for 5-10 minutes. The longer it sits, the more likely it is to start with no problems.

It starts right up if it's 100º or -20º, it's just when it sits for at least a few minutes but not long enough to cool completely. Once it starts it runs great until I shut it off.

All the PCM data looks ok and the fuel pressure is good. Compression is 160 PSI +/- a few PSI on all cylinders. The spark will jump 2+ inches. I've noticed this problem on a number of GM 60º V6s that had "nothing wrong"... I'm wondering if maybe it's a software issue? Has anyone run into this problem before?

Thanks,
Jason

Check for fuel in the press. reg vac hose. Get a fp tester on it and sse if it holds press when shut off.

fuel/injectors leaking. do the full fuel pressure testing procedure.

Check for fuel in the press. reg vac hose. Get a fp tester on it and sse if it holds press when shut off.

Oops, forgot to include that. Fuel pressure drops just a couple PSI in 15 minutes, about 10 PSI overnight.

I removed the vacuum regulator line and plugged it, it doesn't seem to make a difference. It *might* start slightly harder if anything... but very little difference.

I replaced the lower intake manifold gasket 50k miles ago (it was doing the exact same thing then, it hasn't changed at all) and I checked to see if the fuel injectors were leaking at all... they weren't

Oops, forgot to include that. Fuel pressure drops just a couple PSI in 15 minutes, about 10 PSI overnight.

I removed the vacuum regulator line and plugged it, it doesn't seem to make a difference. It *might* start slightly harder if anything... but very little difference.

I replaced the lower intake manifold gasket 50k miles ago (it was doing the exact same thing then, it hasn't changed at all) and I checked to see if the fuel injectors were leaking at all... they weren't

since it is over 10 years old replace the ECT sensor.

let it sit for 5 or 10 minutes or whatever when it wont start, take the rubber air tube off squirt some sensor safe carb cleaner in the throttle body, see if it will start up right away. This should tell if it is fuel or ignition, ... unless it is getting too much gas already, maybe look at the plugs see if they are wet. when ws the last time (mileage wise) you changed your fuel filter.