Do not know what a "twister" muffler is. It may be something that person said to describe what he sells? Most manufactures of performance systems sell what they call "baffled" or "chambered". Depending how a muffler is baffled or chambered effects it ability to reduce noise and increase flow and scavenging in the "EXHAUST SYSTEM". Chambered usually cost more BUT helps in reducing noise, and increasing scavenging. Chambered also will not change over the miles. Baffled mufflers can be baffled with metal and/or fiber material, and WILL change tone/sound over the miles! Either can increase USUABLE power, at the "designers" desired RPM range. Take notice BEFORE you buy at what RPM range that YOU drive YOUR vehicle. Talk to someone at the company about your vehicle, what you will be using it for. My ram is a 1500, reg. cab., long box, 5.7, 6spd auto, 3.55's. I only added a K&N series 63 air intake (63-1561) and a MBRP single tail pipe -cat. back (S5142409) (they say the system has "moderate" sound) to the drive line. other "stuff" to the lighting and cab comfort. I average 16.9 - 17.5 mpg THE WAY I DRIVE. yours will vary. at cruising speed it is almost as quiet as stock, stick your foot into it and the truck "wakes up a bit". Research what you buy so that you get the results that you want. REMEMBER "loud" DOES NOT MEAN increase power, it only has to do with "NOISE LEVEL"! They do not make exhaust pipe out of 6' dia. tubing as it an engine WILL NOT fill the pipe. If it can not fill the pipe it will NOT ad in pulling the exhaust out-which as it comes out it will "draw" the next mixture in.