i have an 08 dodge ram with the 4.7 that i just bought about 2 weeks ago. so far i really like it. i went and had my muffler taken off and dumped right before the rear axle. with the exuast loud now i can realize that some times you can hear the exuast and sometimes you can barely hear it at idle. when i first start it it idles at about 1000-1200 rpm then after a little bit it idles down or when i put it in drive or reverse it idles down. in drive sometimes you can notice a VERY slight surge. what could be causing this? any help would be greatly appreciated! changing a differential bearing this week because i have one howling so if i can find out whats wrong with it to be doing this i would also like to fix this at the same time!