They're rated for 89 octane aren't they? I've put one tank of 87 through the Hemi and it seemed to make it run rather poorly. I figured that would be the case as my dealer told me never to put anything under 89 through it... I don't plan to put another tank of regular in until I get a tuner.. However if you other guys are brave enough to run regular, let me know if that cures the problem. Mine's not bad right now, and not noticable unless I'm looking for it.. Hey man, it's a Hemi, she doesn't like to sit still...

 

there has been other posts about this.. mine idles rough too, but only when the A/C is off, it will run at 500rpms, which is a little low and if you hold the break and just tap the gas LIGHTLY it will stay at about 550, to 600rpms, and will not vibrate, or turn your A/C on.

 

I have 500 miles on my '07 and I have noticed a very slight roughness in the idle. I just assumed that it idles in 4cyl mode. It makes perfect sense to do so and save some fuel. What's the big deal anyways as long as it runs fine when you are off idle? It's a truck anyways, not a luxury car.

 

Do not worry at all about it, if it is only slight and you cannot detect any variation on the tach. If it is more pronounced when the idle drops from 600 to 500 rpm, that is still normal. This is just the nature of the camshaft in the 5.7. Every hemi I have owned has had the same slightly rough idle, but if you listent to the tail pipe outside the truck, you will hear no variation, like you would if there was a misfire. The cams in these engines are already fairly aggressive from the factory, like .460/.470 lift. This will give a slightly lumpy feeling at idle. No worries. Its just the nature of the best. Some smoothness is given away inorder to gain great power. The MDS would surely cause more severe issues if it had to do with any of this. Hope it doesnt bother to much. I like to think of it as i telling you that it wants to go out and play. Enjoy it and try not to worry too much about it.