I have used the Dynomax ultra X Dynomax Performance 17553 - Dynomax Ultra Flo X-Pipe Mufflers - Overview - SummitRacing.com and the price is good, has X pipe built into and is much quieter than I thought it would be and I have used it on 2 different projects the 2nd being a LQ9 with decent sized cam in it and both projects are quiet. louder than stock but inside the cab is nice and pleasant and can hear the radio quite easily with no droning.