Installation went like every set of headers that I have installed in my automotive life. By that I mean that exhaust pipe bending and replacement was required. As I am 68 years old, it is unlikely that I will ever install another set of headers in my life. I have never installed a set that did NOT require major work by the muffler shop to complete the installation. However, they addressed the performance problem I was seeking to correct. The unexpected benefit was a quieter exhaust.
2004 Tundra Access Cab
These are great headers. Install is a B***h though. Passenger side can be done with a socket wobble extension set, some swivel heads, and crowfoot sockets. Take the wheel off and get into it. Lock Tight and torque em down. Driver side is a lot harder. The motor mount really is in the way. I did passenger side 100% torqued to spec and had a shop hook it up (tow it there!) with the driver side only $300. Somebody with more experience than me can do it. Immediate throttle response and deep sounding