So putting a 1uz into a 95 Toyota pickup for offroad racing application. Just getting to the exhaust fabrication portion. I have the ebay tundra headers that i am altering at the collector to run dual exhaust through two high flow obdII cats and into muffler dumped just behind the cab. So my main question is on the tubing sizing. I was thinking 2.5 but am worried about back pressure on the motor etc. If some one could give me some advise on tubing size it would be appreciated.