how to straighten TRD Header flange?

If you can swing it, buy the upgraded down pipe. It uses spring tensioners and a donunt gasket so it can flex and not leak.

If not, the flanges are soft stainless and you can bend the ears with a wrench. The best thing is not to use the crappy TRD copper gaskets. Take the down pipe off and go to a good custom exhaust shop and find some soft metal O ring exhaust gaskets that will fit that flange.

That is what I did after repeated leaks from the crappy gaskets. The soft metal O ring gaskets will crush down and deform and fill any voids and make a good seal. With this type you can tighten the flanges all the way down till they are flat against each other and you won't have any more problems from those connections and the bolts will not come loose either.

They do sell the upgraded Y pipe separately. Call TRD direct and they will give you the correct part number for your year truck and then you can order it directly from your local dealer.

It is the same Y pipe, but they cut the flanges off of the end and welded on slip joints that use a big ball type gasket and it is held under constant pressure with some big springs. That upgrade is what saved the TRD headers from being a total POS. With that mod they are the nicest headers you can get for the 5VZ.