I'm having issues with hesitation when a take off from a stop. Especially when the A/C is on. I'm also suffering from having to down shift on the highway when I encounter hills. I'm only running 31s". I was thinking either a cold air intake or a flash tuner. any suggestions would be great.
I'm considering a left in the near future as well.
She is a 2012 JKU with the 3.6 and a 6 speed

 

What gears are you running? A tuner would probably help out more than the cold air intake, but you need to plan on changing gears in the future. Welcome to the forum.

 

They are the factory gears. If I'm not mistaken they are 3:73. I figured I'd have to re-gear sooner or later. was hoping for the later. Thanks for the input.

 

I would say there is no way they are 3.73's

I have a 2012 with the 3.6l and 3.21's and I was running 33's with no issues. I have an automatic though.

I could be wrong...

 

I'm was told that the automatics came with 3:21 and the straight shifts came with 3:73. But I could have been miss informed.

 

A 3.6 manual, running 31" tires ?

NO, you don't need gears.

You need to realize that you aren't in a sports car. It's a brick with wheels. Any of the cheap bolt-ons or plug-ins will give minimal gains, but may be worth it to you, depending on your budget and expectations.

Next step up would be long tube headers, forced induction, and then a Hemi/LS swap.

 

I am running 315/70R17 with 3.6, and a six speed 3.21 gears. 33 3/4" tires. The only time I hesitate is first thing in the morning when it is cold. It has always done that thought. Even with the original tires.

 

I've never noticed this problem, but it's probably the way I drive. Regardless, others do complain about it, so a company has come out with a fix. Assuming that there's not something mechanically wrong with your Jeep and you're just one of the folks who is sensitive to the hesitation, this may solve it for you ...

Sprint Booster SBJE1012S - SprintBooster Selectable Power Converter for 07-12 Jeep® Wrangler JK, Wrangler Unlimted JK, Grand Cherokee WK/WK2 & Liberty KK with Automatic Transmission - Quadratec

 

That is not the case, regardless of trans, all jk/jkus since 2012 come standard with 3.21s aside from rubicons and willys editions. 3.73s are an option on their own or with the max tow package.
You most likely have 3.21s, regearing to 3.73s would probably help and would work well with 31" tires.

 

I have a 2011 with the optional 3.73. Have zero problems with hesitation at take off. Again, it's not rocket ship but I haven't had any complaints. If you bought brand new and didn't opt for the optional 3.73, you have 3.21.