Sounds like another little advance towards better performance. Speaking of which, I read about high performance "GF" chips and how they increase MPG and performance. Think there kinda BS. Especially for renix era, but I can't talk since I have no real knowledge of them. Any input?

 

100% BS on a Jeep. The 4.0L is already tuned to the max just so Chrysler could keep selling them in face of ever-increasing emissions and fuel economy targets. They eventually discontinued it because the engine couldn't do it. This is the opposite of other engines that are intentionally down-rated. You need to make physical changes before you can mess with the programming.

 

Wanna increase performance?

Have a muffler shop make you a new headpipe without the "crush" in it. It can be done easily, especially if you have a 3" or more lift.

Be sure your distributor is indexed properly. See post # 13 in my pink link.

 

Don't care for better speed, just mpg. Their are a few things in your info I'm not to comfortable to attack on my own, but I do have an extra distributor cap. Did take care of steering box myself (first time) do love working on the jeep, almost as simple as the ****** I had...not really.

 

Those things mentioned above will also help with MPG.

Best way to optimize MPGs:

 

It will actually increase fuel economy. Removing exhaust restriction lets the engine make power easier, which means less throttle/less fuel

 

I did remember reading threads about the dent in exhaust. And once my jeep is on the road: gauges are gonna be an early step, especially tranns temp. Have had bad luck with automatics, even going easy and paying attention. Why did jeep put that dent in again? Thought they used clearence excuse, but an excuse was all it was. Think I'm ready (except money) for smog n Regis. My biggest fear is a bad cat.

 

The actual reason is a "cheap" way to increase back pressure... people assume "clearance" and it gets a pass The effect of the increased back pressure is high EGTs; catalytic converter gets hotter sooner.

 

That's right! Been awhile since I read a thread on that. Won't affect smog pass long as I give enough time to heat the cat, right?

 

Bingo. Old trick of driving on the highway before going in to heat up old clogged cats works too. Emissions testing standards are pretty loose compared to the original new vehicle requirements anyway.