2" or 2-1/4" works well. The LC header is 2" output, stock cat is 2" in/out so I kept it to 2" the rest of the way back (Flowmaster 50 series) since I had enough 2" pipe and fittings left over from from other projects:
- http://www.4crawler.com/4Runner.shtml#Engine

Some folks go with 2-1/4" from the cat back.

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
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