I also have the 18" magnaflow and I love it! It sounds awesome at all speeds, around town, on the freeway. The only complaint would be between 60-65MPH there is slight drone, but it's really not bad at all. There is no difference that I can hear between 4 and 8 cylinders. I have videos of my truck on and off the freeway with before and after sounds. http://www.youtube.com/watch?v=cHKS3...e=channel_page http://www.youtube.com/watch?v=-yT8b...e=channel_page

 

I talked to the guys at Round Rock Muffler (they did my exhaust on my '07) and they recently had a guy have a Flowmaster put on his '08 and it would make a weird popping noise when it dropped into 4 cylinder mode. It would pop every 1 - 3 seconds. They really didn't want to touch my '09 b/c of the trouble he brought them afterwards, even though I was just having my resonators removed.

I had a Magnaflow on my '07 w/ MDS and had no problems. I have removed resonators on my '09 and have no problems. I think this problem is Flowmaster specific and it only happens on maybe 1 out of 10 installs?

 

Well thanks for all the replies guys, seems I have nothing to worry about.
Time to order that Cherry Bomb!

 

The only difference between 8cyl and 4cyl is the volume. When MDS is activated the volume is turned down, on mine it still rumbles but just not near as loud as when in 8....no popping or different tones, still sounds like a truck and to anybody who doesnt know it just sounds like i have a quiter aftermarket muffler. It's actually quite nice because my truck is really loud when in 8 and so it's a good relief when the MDS activates, highway driving is much more enjoyable than other vehicles with aftermarket exhaust i've owned.