Pic for your time. Nearby bakery promoting its wares with death imagery.

I have just discovered that, in certain gears (doesn’t seem to be all of them, primarily 1st and 2nd) my engine starts sputtering at high RPMs. It’s not really a problem per se, but it is disturbing, and combined with synchros that started failing a few months after a transmission rebuild and the lifter noise that started several months ago, sometimes make me wish I had never stumbled into my Jeep addiction.

But setting aside any mental health issues, what in particular should I be investigating? I had severe stalling problems up until about a year ago, when I traced them to problems with the fuel injectors (the engine gets pretty hot, fuel was igniting prematurely and clogging the injectors, so replaced them and wrapped everything with heat shielding).

2005 Jeep Wrangler Unlimited, 4.0L.