If it's got a bad injector, stop driving it until you swap it out. If it's spraying some fuel, but not enough to light off, it'll just wash the oil off the cylinder wall on that one and chew up the rings. The unburned fuel blowing into the exhaust can also cause a cat converter meltdown.
As far as A/C, being undercharged can cause the same symptoms, only it would be cutting out due to the low side pressure being too low.
I've been driving it to work out kinks, bugs, and what have you. It's gone about 30 miles in my care. My dad's decided it's cursed or something and doesn't want to drive it. And, frankly, I prefer driving my Orvis. Plus the Niner isn't street legal at the moment, due to not having it on the insurance, and it being an Oklahoma vehicle.
Point is we're not driving it much. Also, the injector appears to either not be firing at all, or it's stuck open. The fact that it runs well at WOT and high throttle supports the latter, but I try not to assume things are that easy.
As for the A/C, I was able to get my gauge on it. Low side pressure is way too high. Overcharged system.
I told my dad to drive it while I was at work, so he could avoid the broken-*** Chevy. He texted me saying it wouldn't start or run because it was out of gas. Strange, I left a gallon in the tank when I pulled into the driveway after test driving. Also I haven't had any problems starting it today. In any case, I put $20 worth of high-octane into it. My last $20. Still runs fine, considering.