Monty, I'm new here too, and also wondering about chipping the 4.0.
What I understand is that the computer cannot be reflashed, period.
Existing devices are piggyback units that trick the pcm into changing the timing or fueling. Many on the internet say they are not effective. I may try one anyway.
I've recently done some maintenance that really woke mine up. A dirty K&N air filter is horribly restrictive, and no one knows how long it had been since the one on my wrangler was cleaned. First time for me, and I had it since last March.
Also changed plugs, easy job, but the old opnes didn't look bad.
Another biggy was the TV cable to the 3 speed automatic (if you have the OD trans, it's electronic) My TV cable lever at the trans was rusted in place, really screwing up the shift points. Fixing that was a biggie.
That darned 4.0 runs pretty well now, she pulls smartly to redline (would barely hit 4k before and sure took its time getting there!) and kicksdown when she's supposed to.
Before I was trying to decide if I wanted to do a stroker and hesco head, or just drop in a chevy V8. Now I'm not so sure.