Need To Replace My Original 40 Series Flowmasters..with What?

From what I've heard, all flows drone like a beeatch. The super 40s are quieter than the originals, but aren't as bad about drone. If you want something that doesn't drone as much, a good replacement would be SLPs. The LM2s don't have any drone and are pretty tame until you get on it. I've got an o/r h with the LM2 catback and it's fairly quiet at idle and you can cruise around without waking your neighbors, but when you get on it the exhaust sounds real mean. It gets blatty around 3k rpms on a moderate pull, but with a prochamber, it should be pretty smooth. I've heard that the regular Magnaflows are that way as well: docile at idle, tame while cruising and a beast at WOT, though they may be quieter than the LM2s, especially with a prochamber. If you'll be buying the SLPs and the magnaflow mufflers to swap in, just try them both out and see which one fits the bill for you

I hope this helps answer your question