the 4runner had an exhaust leak at both flanges of the catalytic converter. the flanges on the head pipe and intermediate pipe weren't great, and the cat was in poor condition. i ended up purchasing an entire new exhaust system, in stock form, from mostly rock auto, but also toyota overstocks. so, brand new front (head) pipe, new cat, and new muffler/tailpipe assembly (i went with a single-piece unit, rather than getting a new intermediate pipe, muffler, and tailpipe), new cat hanger (that was hard to find), new tailpipe hanger, and new gaskets (both for the cat and for the head pipe at the manifold).

the entire project took only 4 hours, which include removal of the old system, and installation of the new one. i used a grinder to sever the pipe between the cat and muffler, which made getting everything out much easier.

the nice thing about the stock pieces was that everything fit just right. i didn't have to do any bending, stretching, cutting, etc.

and now i've got a leak-free exhaust that is quiet.

edit: added photos - old cat, new cat

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