I have a 98 Expy 5.4 4X4 with 3.73s, 3" air box intake mod w/ K&N, Superchip.

I am looking for the following, if it exists?

-More HP & TQ (low end)
-Better gas mileage
-NOT LOOUD!!! Maybe a bit more than stock.
-No negative scavenging effects
-Single outlet
-Relatively inexpensive


I would like to just do a muffler, is that possible or do I have to do cat back?

Any ideas or success stories?

I have looked into the FlowMaster Delta's but was told by the dealer to go with cat back and 70 series.