Advice needed '98 Cherokee

'98 Cherokee..runs Better when hot outside?

Hi all..

I have a '98 Cherokee with 150k miles which almost none are highway. It has never let me down and is the most reliable vehicle I've ever owned. It always runs ok but is usually pretty slow (stick shift, stock 3.07 gears and 31" mud tires...go figure :greensmok )
My question is this; when the air temperature gets much above 90F and I have the AC on (I don't know if the AC is a contributor or not), the throttle response becomes much improved. That's right IMPROVED. It's almost as if the computer switches to another map when it's hot.
What is wrong with this machine that it won't run like this all the time? Today is one of the hottest days in the last few years and when I backed out of my driveway I actually spun a wheel. I wasn't driving any differently than I usually do.

Thoughts?
It's weird I know:confused1

Lets examine the facts as presented:
Larger tires, presumably lifted.

Modifications not listed? Air box, chip, fan?

It sounds like it likes the air a bit thinner. You could be running a bit rich at cooler temps. The only way to verify that is to sniff it with an O2 meter.

So if it runs, and is no problem, what's the problem?

I can completely understand wanting a vehicle to be at it's peak performance all the time. That said, I have no idea.