Alright, I have a buddy with an 2006 Tacoma V6 5spd, and he is wondering about the different options he has for exhaust. He was asking me about true dual exhaust, and what headers are available for his truck. I havnt crawled under and looked at the stock exhaust setup for his truck, so I dont know what setup Toyota is running these days, I do know my 2003 3.4 from a V6 Tundra (swapped into my 1990 truck) runs two cats, and two o2 sensors (one in front of the first cat, one after the second cat). This makes it very hard to run a true dual exhaust since no matter what it will not be taking a reading from both banks. Im running downey headers, with a full exhaust, and when I was having mine done I did plenty of researching about true dual exhaust, but came to the conclusion after talking to many people and my local trusted exhaust shop that I would lose too much back pressure considering I only have 3.4L of displacement, and would result in loss of low end torque. I explained the theory to my friend, but informed him that this might be a different story since his is a 4.0, im not sure if it is still too small of an engine to benefit from the free'er flowing exhaust, and not hit the fine line of too free flowing a.k.a. loss of back pressure. What are everybodys opinions on this? Also, what headers are available for his truck? What setups are you guys running, and what do you like and dislike about them? What is the legality of the setups (true dual exhaust mainly) since I live in the state of smog nazi's (California).