2006 gz turns but won't start.

[jonathan180iq]

I think you're sniffing the right dog's ass, about vacuum.

You alluded to bad timing on start, which can be marked off easily enough by checking the timing and doing a valve adjust if necessary. But, if that were the case, it would also be difficult to start when rolling it. (Harder than normal, I mean.)

Since she seems to run fine after you get her going, I still feel like it's vacuum. (You mentioned sputter and slightly off at low idle)

Drain the tank down to maybe 1/4 or 1/2 and run a high concentration of cleaner. Like you said, roll start and give her a good stretch. I would even pull those vac lines and blitz the inlets with a shot of the stuff too.

Once that variable is completely eliminated, if it doesn't solve it, you can move onto something else, like the timing.